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A shortbread-like crust, tart rhubarb, and plenty of old fashioned custard filling make these Rhubarb Custard Bars the perfect summer dessert. THM S and low carb
Nope, no clue why half the pan is gone already. Distinctly unprofessional and unphotogenic, I know.
The inspiration for this recipe
This recipe was born in Ohio when I was living with my grandparents while helping at The Peach Barn in Holmes County many summers ago. Grandma often threw together a quick rhubarb custard dessert.
The rhubarb for this particular batch of rhubarb custard bars came from my great aunt Mary Lou (Grandma’s sister) in Holmes County!
New and improved
This recipe was first published to the blog in 2015. Since then I revamped it using my baking mix and included that version in Necessary Food, my first cookbook. (Find the recipe on page 335.) You can find the original blog recipe at the bottom of this post.
This updated recipe (2021) has a sturdier crust and holds its shape better when cut into bars. This recipe also has more custard (always a good thing) and is made in a square 8″x8″ pan instead of a pie plate. Again, more conducive to the title, “Rhubarb Custard BARS.”
I wouldn’t try making this updated recipe in a pie plate. It may not fit anymore due to the additional custard.
How to choose and prepare rhubarb
Thin stems of rhubarb are best. Split large stems down the center before chopping. Discard any woody stems. Chop the rhubarb fairly small so it can soften within the baking time – a quarter inch to half an inch is good.
I have not tried this recipe with frozen rhubarb, but from what I’ve researched, frozen rhubarb should work as well. Thaw and drain before measuring and proceeding with the recipe.
I like to taste the tartness of the rhubarb so I didn’t go overboard on the sweetener. This amount tastes balanced to me – not overly sweet – but add more if you like. Many people do like more sweetener in recipes than I do.
As always, check out the Notes section of the recipe for helpful info and answers to frequently asked questions!
You may also enjoy:
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STARTING THM
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MY RECIPE INDEX
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RECIPE INDEX BY FUEL TYPE/ALLERGY/THEME
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Coconut Cream Pie Delight
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Basic Custard (Pudding)
Blueberry Custard Bars
These Blueberry Custard Bars are very similar to the Rhubarb Custard Bar recipe in Necessary Food made with my baking mix.
Rhubarb Custard Bars
- Total Time: 56 minutes
- Yield: 9 servings
Description
A shortbread-like crust, tart rhubarb, and plenty of old fashioned custard filling make these Rhubarb Custard Bars the perfect summer dessert. THM S, low carb
RHUBARB NOTE: Thin stems of rhubarb are best. Split large stems down the center before chopping. Discard any woody stems. Chop the rhubarb fairly small so it can soften within the baking time – a quarter inch to half an inch is good.
I like to taste the tartness of the rhubarb so I didn’t go overboard on the sweetener. This amount tastes balanced to me – not overly sweet – but add more if you like. Many people do like more sweetener in recipes than I do.
Ingredients
CRUST:
- ¼ cup coconut flour
- ¼ cup oat fiber
- 1 ½ teaspoons THM Super Sweet Blend
- 4 tablespoons salted butter (melted)
- 1 egg
CUSTARD:
- 3 eggs
- ¾ cup heavy whipping cream
- 3 tablespoons oat fiber
- 1 ½ tablespoons THM Super Sweet Blend (or more, to taste)
- 1 teaspoon vanilla extract
- 1/8 teaspoon salt
4 cups chopped fresh rhubarb (see note above)
Instructions
CRUST: Mix the crust ingredients with a fork or a hand mixer until a smooth dough forms. Press into the bottom of a greased 8”x8” pan and prebake at 350*F for 6 minutes.
CUSTARD: Whisk the eggs until smooth. Add the cream, oat fiber, sweetener, vanilla, and salt and whisk until smooth.
ASSEMBLY: When the crust is done baking, spread the chopped rhubarb evenly over the hot crust. Gentle pour the custard over the rhubarb and make sure everything is fairly level.
BAKE at 350* for 30 minutes or until loosely set. The custard should jiggle slightly in the center when you move the pan but not appear liquidy. It will continue setting as it cools.
SERVING: The rhubarb custard bars are ok warm (especially if you don’t mind the egginess of custard) and would be great with some sugar free vanilla ice cream melting over them, but I prefer them completely chilled. When chilled they set up nicely and hold their shape. I like to cut the bars into 9 squares and serve with a dab of Reddi-wip.
Notes
Oat fiber: This versatile low carb flour can usually only be found online. Not all brands are created equal, but I like LifeSource oat fiber. Use gluten free oat fiber for a gluten free option. Oat fiber and oat flour are different and are not interchangeable.
Sweetener: Feel free to use your favorite low glycemic sweetener to taste in place of the THM Super Sweet Blend.
Fresh vs frozen rhubarb: I have not tried this recipe with frozen rhubarb, but from what I’ve researched, frozen rhubarb should work as well. Thaw and drain before measuring and proceeding with the recipe.
Allergy info: Gluten free (use gluten free oat fiber). Nut free. Most people with tree nut allergies can have coconut products, but confirm with your doctor first.
UPDATED: This recipe was first published to the blog in 2015. Since then I revamped it using my baking mix and included that version in Necessary Food, my first cookbook. (Find the recipe on page 335.) You can find the original blog recipe at the bottom of this post.
- Prep Time: 20 mins
- Cook Time: 36 mins
- Category: Dessert
- Method: Bake
- Cuisine: THM S, low carb, sugar free, gluten free
Keywords: trim healthy mama, thm, low carb, sugar free, gluten free, nut free, low carb rhubarb recipes
Rhubarb Custard Bars (original blog recipe – 2015)
6-8 servings | THM XO or S (depending on which flour you use)
CRUST:
- 1 cup oat flour (XO) or almond flour (S)
- 3 tablespoons xylitol (or another sweetener that measures like sugar)
- 1/4 cup salted butter (cold and cut into chunks)
FILLING:
- 1/2 cup heavy whipping cream
- 2 small eggs
- 3 tablespoons oat flour (XO) or almond flour (S)
- 2 tablespoons Truvia (or 1 tablespoon THM Super Sweet Blend) – or more to taste (I like mine tart)
- Dash of vanilla extract
- Pinch of salt
4 cups chopped fresh rhubarb
INSTRUCTIONS:
- Combine the crust ingredients with a pastry cutter until they resemble coarse crumbs, then press into a greased 9-inch pie plate and bake at 350* F for 10 minutes. Set aside to cool for at least 10 minutes while preparing the filling.
- Beat the heavy whipping cream, eggs, flour of choice, sweetener, vanilla, and salt until smooth. Stir in the fresh rhubarb. Pour this mixture over the slightly cooled crust and return the pan to the oven for 25-30 minutes or until it is set all the way through. Let sit a little before cutting so it can firm up. Feel free to serve this with one of my homemade ice cream recipes!
- Serves 6-8. I’m sure you could double this recipe for a 9″x13″ pan.
NOTE:
Most people will probably want more sweetener than this recipe calls for. As you’ll notice in the updated recipe above, even I prefer a little more sweetener these days. 🙂
Allergy info: Gluten free (use gluten free oat flour). Nut free if using the oat flour option.
I want to be polite yet must be honest y- this recipe tasted awful. The oat fiber has a cardboard – like flavor and the custard was bland. I reduced the amount of rhubarb by one cup as it was plenty and sprinkled some cinnamon and a dash of nutmeg on top but it did not help cover the taste of the oat fiber in it. I had to toss the entire dish out . Sorry.
I wonder what brand you were using. Some brands, like NuNaturals are very cardboardy. Other brands, like LifeSource, don’t have much flavor at all.
Do you think these would freeze well?
No, I don’t think I would freeze a custard type dessert. I imagine it would be kind of soggy once thawed.
I’ve had this recipe in mind to make one of these days so this is perfect! Also, what I really wanted to say is- STUNNING photography!
Thank you! <3 The photography is one of my favorite parts of blogging. The roses were courtesy of my husband and they matched perfectly!
Rhubarb is popping up here in Ontario Canada. I used your baking blend, 3 tbsp erythritol along with a squirt of my stevia liquid and baked it in a square 8 inch glass dish . Fabulous. Also, I saved about a 1/3 of a cup of the crust and sprinkled it on the top. So appreciate your recipes!
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Have you ever tried oat fiber or baking blend, if so how was it and what is the measurement?
No, I’ve just tried it with almond flour or oat flour. Baking Blend and oat fiber are both drier than oat flour and almond flour, so you’d need less of them if you decide to try that.
Nutritional value?
I don’t usually calculate nutrition info on my recipes since the healthy eating lifestyle I follow doesn’t require it (Trim Healthy Mama), but MyFitnessPal is a super easy way to find nutrition facts! If you sign up for an account, under the Recipes tab there’s a place where you can just add the link to a recipe and it will pull up the ingredients for you to confirm, then generate the nutritional info! 🙂
In the cookbook you asked us to share with you changes that we’ve made and how they turned out. This recipe is one that had to be adjusted for ingredients on hand (I’m not going out in a blizzard just to buy cream). So,
I made your baking mix and used that as directed. I don’t have a 9″ pie plate so I used my biggest one of 8″. I set aside the 3 T of crumbs, but had to use them for the middle of the pie. I didn’t have full fat cream and substituted 1/2 + 1/2. As I am fuel cycling, I don’t have any whole eggs in the house at the moment and used egg whites only.
As result of those changes, the following adjustments needed to be made.
– mix custard until fully blended
– put thawed, drained rhubarb pieces in the warm crust
– pour custard on top
– bake at recommended temperature, but for 35 minutes instead of 25
I am also baking at 4400 feet above sea level.
Turned out GREAT!
Thanks for sharing, Sandi! I’m glad it worked for you!
We use rhubarb with strawberries since they come in season at the same time in Michigan. We also freeze the rhubarb cleaned and cut up to go with strawberries to make crisps. We have used the oat flour and Truvia. Glad you have had a chance to try something new.
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Great idea!
Not bad! I’ll have to try it the other way. I’m not much of a “custard” person ~ so I may try some of the crust crumbled on top or something ~ but, good! 🙂
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I’m glad it turned out for you! I like the idea of saving some of the crust for the top!
I put the oat bran in the food processor! 🙂 I’ll see how it works ~ just didn’t want to waste it! Thanks again!
No problem – sorry I can’t be of more help! Let me know how it turns out! I believe that oat bran is an E, so you’d have a crossover using it in these bars (just like if you would use oat flour). PS – you probably already know this, but you can make oat flour by just grinding up oats in a blender or food processor. 🙂
🙂 It’s in the oven ~ I’ll let you know! 🙂 Of course, I have nothing to compare it too ~ I’ll have to make it the other way when more rhubarb grows or we find some! 🙂 OK ~ thanks! LOL! Thank you! I knew I had seen something like that, but, didn’t remember what! With Old Fashioned Oats, Oat Fiber, Oat Flour, Oat Bran ~ I couldn’t remember what I had seen! 🙂
Still impressed with your knowledge at a young age! 🙂 I just need to start trying more healthy things ~ new things! 🙂 I knew I had seen a rhubarb recipe on here once ~ I love rhubarb! I wondered once if it would be on plan! 🙂
Hi! I accidently got Oat Bran instead of Oat Fiber the one time. Can I use the Oat Bran in this recipe instead of the Oat Flour?
Hi Tammy! I’ve never actually seen or tasted oat bran, so I’m afraid I’m not sure what the taste and texture are like.
Hi Briana! I thought I had Oat Flour, but, I got the Oat Fiber to make your baking mix! 🙂 I accidently got the Oat Bran one time and had a bag sitting here! 🙂 Thank you! Hope you’re doing good! 🙂
Could you make this with the THM Super Sweet blend or even the Gentle Sweet blend or does it have to be equal amounts to regular sugar like you posted in the recipe?
Any low glycemic sweetener should work, but since both Super Sweet Blend and Gentle Sweet are more concentrated than xylitol, you’ll have to adjust amounts to taste. 🙂 You can use this conversion chart to help: http://www.trimhealthymama.com/main-home/sweetener-conversion-chart/
Awesome! Thanks so much! Loving all you recipes so far so I am super excited to try this one! I got an enormous patch of rhubarb in my yard. So big that I can freeze it and still have to give oodles away! Very blessed! Now I just need to find more THM Rhubarb recipes. 😉
Wow, that is a blessing! I would love to be able to grow rhubarb, but it just doesn’t do too well down South. I actually just bought some from the grocery store the other day and have been working on using it in some recipes for my cookbook. 🙂
Hi Briana! This recipe looks amazing…I love all things rhubarb 🙂 Is this dessert more runny or does it firm up after cooling? My mom makes a wonderful rhubarb custard, and I would like to try it using thm ingredients.
Yes, it sets up like a custard. 🙂
Just an update….I made a double batch of these this morning with the thawed, drained rhubarb. They turned out great! 🙂
Awesome! Thanks for letting me know! Did you use the oat flour or almond flour option?
I have a whole bunch of frozen rhubarb in the freezer I would like to use up. Do you think I should thaw and drain if I am using that?
I’ve never used frozen rhubarb so I’m not sure how it acts, but yes, I would thaw and drain it. 🙂
I was going to ask this! So glad someone has tried cuz these sound amazing and I haven’t seen fresh rhubarb yet!
This sounds yummy! My dad loves rhubarb pies, so I might try making these for him. 🙂
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This looks so good Brianna, do you think to keep it an “S” that we could use the crust from your Strawberry delight if I didn’t bake it as long the first time and then poured in the rhubarb filling and finished the baking? Or would it become soggy? Sometimes almond flour crusts are just so overpowering….or maybe use 1/2 of the new baking blend and half oats? Just thinking outloud…. thanks…I value your opinion and expertise so much! I appreciate all you do to make our THM lives easier and better!
Using the delight crust is a great idea! I’m not sure about the sogginess, but the rhubarb layer is meant to soak into the crust somewhat. The baking blend idea would probably work as well.
Thanks..I’ll try this with the delight crust and we’ll see how it goes….I loved the crust when I made the delight (thanks sooo much for the recipe!) and I thought it was very cookie-like…should be good with this…I’ll let you know!
That’s funny…I thought the same thing about it tasting like cookies. I’m intending to work with it in that capacity when I get home this fall (I’m working out of state for the summer and basically don’t have a kitchen).
Briana, I will try this for sure. Just got me a bunch of Rhubarb from the garden. I am so looking forward to hearing how to replace the crust with Baking Blend. I am not one to tested myself. Thanks again for all the great postings! enjoy your summer at your grand parents.
Thank you, Ursula!
I grew up in OH, but I have never tried cooking with rhubarb. These look so delish! You make them look tasty by the way you present them. Such a great job with the photos!! God bless you, Briana!
Thank you, Cheryl!