This gorgeous upside-down rhubarb cake drapes buttery rhubarb over a vanilla-scented cake for a spring treat. Serve it plain or with a little whipped cream.
Silky soft rhubarb is obviously the star of this humble upside-down rhubarb cake, but I'd argue in favor of the cake itself. Spelt flour, my favorite whole grain flour, gives it a tender crumb and a lovely, rustic texture.
Plus, the prep time is less than half an hour, producing a gorgeous blend of sweet cake and slightly tart rhubarb that, if done right, caramelizes just the tiniest, crispiest bit along the edges.
This cake is so good warm, but it's also delicious straight from the fridge (ask me how I know). It's a beautiful way to celebrate spring and this special vegetable that acts like a fruit.
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Why I Love This Rhubarb Cake
The bold, unique flavor of rhubarb is the standout of this cake, and I love it for that. This is a no fooling around rhubarb cake, with a whole 1 pound layered across the bottom of the buttery cake, so you'll truly taste it. When rhubarb season rolls around each year, I'm making as much use of it as I can. This cake is a highlight of my spring baking. You'll love that it's:
- Easy and reliable. A butter cake (but with whole grain flour) forms the base of this pretty cake, and it comes together in just minutes with no fuss needed.
- Packed with rhubarb. If you are a rhubarb lover like me, you'll love how much it features in this cake.
- Nicely balanced. A hint of tartness remains despite the sweetness of the cake, and I love how those contrasts play out.
Ingredients You'll Need
Make sure to scroll down to my recipe card at the bottom of this post for the full ingredient amounts and instructions!
- Brown sugar - Light or dark brown sugar is fine (I used dark brown sugar).
- Butter - You'll need unsalted butter for the topping and for the cake.
- Rhubarb - Choose firm, unblemished stalks of rhubarb for the best results. It's OK if the rhubarb is green, but if you want a pinker topping, choose pink or reddish rhubarb.
- Spelt flour - You can use all-purpose flour if you prefer, or whole wheat pastry flour.
- Baking powder
- Salt - I always use fine sea salt or table salt.
- Granulated sugar
- Egg - A large or extra-large egg works.
- Milk - I use whole milk, and 2% is also fine.
- Vanilla - Use pure vanilla extract or vanilla bean paste.
How to Make Upside-Down Rhubarb Cake
Here's a preview of how you'll make this sweet little cake, with the full instruction details in the recipe card lower down.
1. Prep rhubarb: Melt honey and butter in a skillet, then add rhubarb.
2. Cook rhubarb: Saute the rhubarb until slightly softened.
3. Make dry mix: Whisk together the dry ingredients.
4. Cream butter: In a large bowl, cream the butter and sugar, then add the egg and vanilla.
5. Combine: Mix in the flour mix and the milk, alternating between each addition.
6. Add rhubarb to pan: Line an 8-inch baking pan with parchment and arrange the rhubarb on the bottom.
7. Add batter: Spread the batter over the rhubarb.
8. Bake: Place in a 350°F oven and bake for 45 minutes, then cool.
Baking Tip: Lots of Rhubarb!
I call for a lot of rhubarb to make this cake, a whole pound to be exact. If you love rhubarb, you can add a bit more, up to 1 ½ pounds. The rhubarb will cook down a bit as it sautes, so I don't think you'll find it to be too much.
Recipe Notes
- Make the batter while the rhubarb cooks. As the rhubarb simmers, put together the batter (keeping an eye on the cooking rhubarb, of course). This will save you a few minutes, as they'll both be done in about the same amount of time.
- Line the pan with parchment. Line your baking pan with parchment paper for easy removal when you turn out the cake.
- How to cook the rhubarb: I like to cook the rhubarb until it's quite soft so that it melts into the top of the cake a bit. You can keep the rhubarb more firm by cooking it slightly less, until it's just tender but not soft.
- Gently add the batter. The batter is thick, so you'll want to carefully dollop it on top of the rhubarb spread out in the pan. Use a rubber spatula or offset spatula to smooth it out evenly.
- Add citrus zest. For extra flavor, zest in 1 organic lemon or 1 organic orange (orange is a classic flavor pairing with rhubarb).
- Make it strawberry-rhubarb. Add ½ pound of sliced strawberries to the cake pan after you add the cooked rhubarb (you won't need to pre-cook the strawberries) to make this into a strawberry rhubarb cake.
Proper Storage
- Fridge - I like to keep this cake in the fridge because during the warmer months it will stay fresher longer. Let it sit on the counter for 10 minutes before serving if you like, although it's lovely eaten cold. Cover the cake with foil or place it in an airtight container and store it in the fridge for up to 5 days.
- Freezer - Let the cake sit in the fridge for 30 minutes to firm up the topping, then wrap it (or individual slices) in plastic wrap, then foil, and store it in the freezer for up to 2 months. Thaw the cake overnight in the fridge before serving.
If you tried this recipe please let me know! Or if you have any recipe questions, always feel free to reach out in comments or email. I hope you love it! ❤️
Recipe
Upside-Down Rhubarb Cake
Ingredients
For the Rhubarb
- ½ cup brown sugar light or dark brown sugar
- 4 tablespoons unsalted butter
- 1 pound rhubarb , washed, trimmed, and sliced into long ¼-inch pieces (the pieces should be about the length of your cake pan)
For the Cake
- 1 ½ cups spelt flour or all-purpose flour
- 1 ½ teaspoons baking powder
- ¼ teaspoon fine sea salt
- ½ cup unsalted butter , at room temperature
- 1 cup granulated sugar
- 1 egg
- 1 teaspoon pure vanilla extract
- ½ cup whole milk
Instructions
Cook the Rhubarb
- In a large cast iron pan or skillet, melt the ½ cup brown sugar and 4 tablespoons unsalted butter over low heat. Spread the 1 pound rhubarb out evenly and cook until slightly softened and releasing its juices, about 5 minutes. Remove from heat.
Make the Cake
- Heat oven to 350℉. Butter a 9-inch round cake pan and line it with a circle of parchment. Arrange the cooked rhubarb evenly across the bottom of the pan and set aside.
- In a small bowl, whisk together the 1 ½ cups spelt flour, 1 ½ teaspoons baking powder, and ¼ teaspoon fine sea salt.
- In a large bowl and using an electric mixer on medium speed, cream the ½ cup unsalted butter, scraping down the sides of the bowl as necessary, until the butter is lighter in color, about 45 seconds. Then add the 1 cup granulated sugarin a steady stream and scrape down the bowl again. Continue to mix on medium speed until the mixture is very light in color and texture, about 4 minutes.
- Beat in the 1 egg and 1 teaspoon pure vanilla extract, mixing well to combine.
- With the mixer on low, add the flour mixture in two doses, alternating with the ½ cup whole milk. Scrape down the sides of the bowl in between additions.
- Pour the batter on top of the rhubarb, smoothing it gently. Place the cake in the oven and bake for 25 to 35 minutes, or until a toothpick inserted in the center comes out clean.
- Remove from the oven and set on a rack to cool for 10 minutes. Run a butter knife around the side of the pan to loosen the cake, then turn out onto the rack to finish cooling completely.
Notes
- Make the batter while the rhubarb cooks. As the rhubarb simmers, put together the batter (keeping an eye on the cooking rhubarb, of course). This will save you a few minutes, as they'll both be done in about the same amount of time.
- Line the pan with parchment. Line your baking pan with parchment paper for easy removal when you turn out the cake.
- How to cook the rhubarb: I like to cook the rhubarb until it's quite soft so that it melts into the top of the cake a bit. You can keep the rhubarb more firm by cooking it slightly less, until it's just tender but not soft.
- Gently add the batter. The batter is thick, so you'll want to carefully dollop it on top of the rhubarb spread out in the pan. Use a rubber spatula or offset spatula to smooth it out evenly.
- Add citrus zest. For extra flavor, zest in 1 organic lemon or 1 organic orange (orange is a classic flavor pairing with rhubarb).
- Make it strawberry-rhubarb. Add ½ pound of sliced strawberries to the cake pan after you add the cooked rhubarb (you won't need to pre-cook the strawberries) to make this into a strawberry rhubarb cake.
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