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Rhubarb Custard Bars

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5 from 4 reviews


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.





4 cups chopped fresh rhubarb (see note above)


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.


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