This recipe for keto rhubarb upside-down cake features a perfectly caramelized rhubarb topping and a moist buttery almond flour cake. If you’re looking for creative ways to use rhubarb this old-fashioned cake is a must-try.
It’s easy to see that we are huge fans of all things rhubarb, just take a look at our collection of keto rhubarb recipes if you have any doubt.
However, I’ll admit that I was a bit intimidated about creating a keto-friendly rhubarb upside-down cake that would prove to be a great alternative to its high-carb counterpart.
I have made countless upside-down cakes in my day, but a keto rhubarb one? Well, let’s just say it was time I rolled up my sleeves and just go for it and stopped coming up with excuses of why it couldn’t be done.
Thankfully, making a low carb rhubarb upside down cake was NOT hard at all. I can’t wait for you to grab some rhubarb and try this classic cake recipe.
If you’re a fan of cakes, be sure to also check out our collection of keto cakes, where you are sure to find some new favorites.
Keto Rhubarb Upside Down Cake
I took inspiration from the pineapple upside cake I used to make for my family and gave it a keto makeover.
By using almond flour instead of wheat flour and swapping the sugar for a sugar substitute I was able to transform this into a gluten-free, sugar-free upside-down cake that could fool even the most discriminate palate.
Although I love the pairing of strawberries and rhubarb, I chose to highlight rhubarb’s tartness knowing that it would contrast beautifully with the sweetness of the brown sugar substitute and the buttery flavor of the almond flour cake.
I chose to make it in a cast-iron skillet because it helps with the caramelization process. But you can, however, also bake in a 10-inch cake pan.
Is Rhubarb Keto-Friendly?
If you didn’t know, rhubarb is actually a vegetable in the same family as sorrel. but due to its tartness, it’s used often in desserts and combines well with other fruits.
As far as flavor goes, it reminds me of tart apples with a hint of berries.
So you may be asking, is rhubarb keto? The great thing about its tartness is that it means it’s not very sweet! In fact, a 1/2 cup serving of rhubarb contains only about 1.7 net grams of carbs making it low in carbs and keto-friendly!
This means there are less than 2 carbs in a rhubarb serving!
What’s more, rhubarb is a great source of antioxidants, fiber, and vitamin K. It’s even being called by some the next “superfood”.
So finding ways to include it into your keto diet like this recipe for upside-down cake doesn’t just make delicious treats but it’s also good for you!
If you’re asking “can you eat rhubarb on keto?”, the answer is a resounding yes.
Ingredients You’ll Need To Make A Rhubarb Keto Upside Down Cake
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Note that the full printable recipe is at the bottom of the page.
How To Make A Keto Rhubarb Upside Down Cake
This keto-friendly upside-down cake is made similarly to the traditional recipe. You start by pre-heating the oven to 325 degrees. Note that the temperature is a little lower than most cake recipes. This is to ensure the topping has to caramelize but not burn.
In a large bowl, you will toss the sliced rhubarb with some of the brown sugar substitute and a tiny amount of xanthan gum. The xanthan gum is optional but it does help the topping to thicken as it cooks.
Next, using a 10-inch cast-iron skillet you’ll mix the butter, salt along with the brown sugar substitute and cook over over medium heat. The mixture should be whisked until smooth and bubbling. This will take anywhere from two to three minutes.
At this point, you’ll add the prepared rhubarb into the cast-iron skillet and stir being sure to cover the rhubarb with the butter and brown sugar substitute mixture.
Now it’s time to make the cake batter. Something to note is that the batter itself does not have any sweetener. This is because the topping that has all the sweetener will seep into the cake as it bakes.
Not adding additional sweetener ensures that the upside cake isn’t cloyingly sweet.
When the batter is complete, you’ll spread the cake batter to the top of the rhubarb mixture in the cast-iron skillet. The cake is then baked 40-50 minutes, or until the top of the cake is lightly browned and the cake is firm to the touch.
After the keto rhubarb upside cake is baked it will need to cool slightly before attempting to flip the cake onto a plate.
How To Flip An Upside Down Cake?
Once the cake is baked it will need to cool for about 15 minutes on a wire rack. Then using a sharp knife, run the blade along the side of the cake to help release the upside-down cake.
It’s important to remember to release the cake while it is still warm to prevent it from sticking to the pan. Do not allow the cake to cool longer than 15 minutes because the cake will stick to the bottom of the pan.
To flip the cake, use oven mitts and place a serving plate on top of the cast-iron skillet or cake pan. Hold the cake pan firmly and invert quickly onto the plate.
Lift the plate and if any of the toppings stick to the pan, firmly tap on the bottom of the cake pan with the back of a knife or wooden spoon. Use a spatula to pat any topping that remains stuck to the bottom of the pan and place it onto the cake.
The Best Sugar Substitute For Keto Rhubarb Upside Down Cake
When it comes to choosing which sugar substitute to use for this sugar-free upside-down cake, I have several for you to choose from.
although you can use their white granulated sweetener exclusively it will not have the same depth of flavor.
Having said that, I’m also partial to the brand Swerve brown sugar which is an erythritol blend. Similar to Lakanto it uses sugar alcohols and has a 0 % impact on blood sugar.
Surkin gold is another delicious substitute for brown sugar and one I have also used. I find the texture of Surkin is closest to traditional brown sugar.
And don’t forget to check out our entire collection of keto cakes.
Also, check out our Amazon Store for our recommendations. You might be surprised by how many great keto options are at your disposal.
Grab Our Books
In case you didn’t know we have authored two books for you, Essential Keto Bread and Essential Keto Desserts both inspired by your requests over the years. It’s my prayer these keto cookbooks will help make keto a delicious breeze for you.
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Keto Rhubarb Upside Down Cake
- 2 cups of almond flour finely milled, measured, and sifted
- 1/2 cup and I tablespoon of of brown sugar substitute
- 2 teaspoons of baking powder
- 1 1/4 teaspoon of sea salt
- 1/2 teaspoon of ginger powder
- 3/4 cup unsalted butter
- 1 cup of sour cream
- 2 eggs
- 1 pound of fresh rhubarb, rinsed and sliced into 1/2 inch pieces about 3 1/2 cups
- 1/4 teaspoon of xanthan gum (optional)
- Pre-heat oven to 325 degrees
- Rhubarb topping: In a medium-sized bowl toss the sliced rhubarb with 1 tablespoon of brown sugar substitute and the 1/4 teaspoon xanthan gum. Set aside.
- Cake batter dry ingredients: In a large mixing bowl, combine the measured and sifted almond flour, baking powder, and sea salt. Set aside.
- Using a 10-inch cast-iron skillet cook over medium heat on the stovetop the 1/4 cup of butter, 1/4 teaspoon of sea salt along with 1/2 cup and brown sugar substitute. Whisk the mixture until smooth and bubbly, about 2-3 minutes. Turn off the stove and set it aside.
- Add the prepared rhubarb topping to the cast-iron skillet along with the butter mixture and stir well being sure to cover the rhubarb with the butter and brown sugar substitute mixture.
- Proceed to finish the cake batter. Melt the remaining 1/2 cup butter and set it aside to cool.
- Cake batter wet ingredients: In a medium-sized bowl, stir the cooled melted butter, sour cream, and eggs until they are well combined.
- Fold the butter and sour cream mixture into the batter dry ingredients. Mix until well incorporated. Note that the cake batter does not have any sweetener, this is intentional since the sweet rhubarb topping will seep into the cake as it bakes and sweeten the cake.
- Spread the cake batter to the top of the rhubarb mixture in the cast-iron skillet.
- Bake for 40 minutes to 50 minutes, or until the top of the cake is lightly browned and the cake is firm to the touch.
- Place the cast-iron skillet on a wire rack, and cool slightly for 15 minutes. Then run a sharp knife along the sides of the cake to help release the cake. Place a large plate over the top of the pan and quickly turn it upside down. It's important to remember to release the cake while it is still warm to prevent it from sticking to the pan.
- Lift the plate and if any of the toppings stick to the pan, firmly tap on the bottom of the cake pan with the back of a knife or wooden spoon. Use a spatula to pat any topping that remains stuck to the bottom of the pan and place it onto the cake.
- Store leftovers in the refrigerator for up to 5 days or freeze for up to 3 weeks.
This rhubarb upside-down cake can be baked in a 10-inch cake pan. To do so you will need to grease the cake pan well with butter on all sides and bottom. Then in a skillet pan over medium heat, mix 1/4 cup of butter, 1/4 teaspoon of sea salt along with 1/2 cup and brown sugar substitute, and cook the mixture whisking at all times until smooth and bubbling, about 2-3 minutes. Add the butter mixture to the bottom of the greased cake pan and then add the prepared rhubarb to the top of the butter mixture. Once this is done you will add the cake batter to the top of the cake and bake for 40-50 minutes.
The recipe calls for a brown sugar substitute but if you can also opt to use a granulated sugar substitute if that is not easily available.
Nutrition Information:Yield: 12 Serving Size: 1
Amount Per Serving: Calories: 275Total Fat: 25.21gSaturated Fat: 10.7gTrans Fat: 0gCholesterol: 66mgSodium: 112mgCarbohydrates: 6.6gNet Carbohydrates: 3.8gFiber: 2.7gSugar: 0.5gProtein: 6g