Rhubarb sheet cake is one of those simple homemade desserts that always brings back warm memories for me. I love settling in with a slice and a cup of hot tea, especially on a quiet afternoon when I actually have time to slow down. The soft cake and pleasantly tart rhubarb make such a lovely combination, and this version is made without added sugar.

Why sugar-free?
Well, why use sugar if you can achieve the same level of sweetness without it?
Ever since we removed sugar from our meals, I have been experimenting with our favorite recipes to see if they could be kept on our menu with some adjustments (check our Cinnamon Brioche Rolls, for instance). This is one of the "survivers" we incorporated into our sugar-free menu by replacing sugar with allulose. It doesn't always work, but it does perfectly for this recipe.
If you don't have allulose, feel free to use monk-fruit sweetener or a blend of both. However, allulose usually works best for baked products.
This recipe is a variation of my all-time favorite apple sheet cake recipe.

Ingredient Notes
To make this rhubarb flatbread, you'll need the following ingredients.

Rhubarb season is far too short, so I always keep bags of chopped rhubarb in the freezer to enjoy throughout the winter. When I'm ready to use it, I thaw it only slightly - just until the pieces begin to separate - rather than defrosting it completely, which helps prevent excess moisture.
This sheet cake recipe is sugar-free. However, if you're not following a sugar-free diet, feel free to replace allulose with regular sugar in a 1:1 ratio.
Allulose is my go-to choice for sugar-free cakes, including my favorite lemon mousse tart. However, it might not be available in your region, as in the case of the EU. If you can't find allulose, monk fruit sweetener is a great alternative.
Step-By-Step Instructions

Start by making the crust: combine all the ingredients of the crust in a large bowl, using your hands or a stand mixer.

It's great to make the dough with your hands by putting all your love into the process and feeling how flexible and responsive the dough is to your touch. 🙂

Spread the dough onto a lined baking tray. The measurements of our baking tray are 13x15 inches, and this recipe will give you a nice thin crust with this tray size. Preheat the oven to 355 ℉ (180 ℃).

Meanwhile, prepare the rhubarb cream: remove the skin from the rhubarb and chop into ~0.5x0.5 inch pieces.

Take a medium-sized bowl and combine all the ingredients of the cream until smooth and uniform.

Spread the chopped rhubarb evenly over the crust. Pour the cream mixture over the crust. Alternatively, add the chopped rhubarb directly to the cream mixture and stir well before pouring over the crust.

Sprinkle with cinnamon.

Bake for 50 minutes (or until golden brown).


Sugar-Free Rhubarb Sheet Cake
Ingredients
Crust
- 7 oz (200 g) butter
- 3 oz (85 g) sour cream
- 1 teaspoon baking powder
- 3 ¼ cups (400 g) wheat flour
Cream
- 18 oz (500 mL) sour cream
- 1 egg
- 1 glass allulose
- 21 oz (600 g) rhubarb
- 2 teaspoon cinnamon powder (optional but highly recommended)
Instructions
Prepare the crust
- Either by hand or using a stand mixer, combine the ingredients of the crust. The dough needs to be uniform, non-sticking, and rather flexible.
- Take a baking tray, lined with parchment paper, and spread the dough evenly.
Prepare the cream
- In a medium-sized bowl, combine the ingredients of the cream until smooth and uniform. Make sure there are no clumps from the flour.
- Chop rhubarb rather finely (~0.5x0.5 inch) and mix with the cream.
Bake the flatbread
- Preheat oven to 355 ℉ (180 ℃). Distribute the rhubarb cream evenly on the surface of the crust.Sprinkle with cinnamon.
- Bake for 50 minutes.
- Let it cool slightly and serve.
Video
Notes
- If the dough tears easily and isn't flexible, it means there's too much flour in it. If the dough is sticky and rather wet, add a little more flour.
- For best results, when spreading the dough onto the baking tray, shape a small edge all around it to prevent the cream from touching the sides of the tray.
- The same recipe can be made with apples, raspberries, and other fruits or berries that are on the tart side.
- This flatbread tastes incredible on the first day and is even better the next day when stored in the fridge. It only gets better!
- You can use either fresh or frozen rhubarb. If using frozen rhubarb, thaw it only slightly - just until the pieces begin to separate - rather than defrosting it completely. This helps prevent excess moisture.






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