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An upside-down rhubarb cake on a white plate.

Upside-Down Rhubarb Cake

5 from 1 vote
This gorgeous rhubarb upside-down cake drapes buttery rhubarb over a vanilla-scented cake for a beautiful, summery treat.
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Prep Time 15 minutes
Cook Time 35 minutes
Total Time 50 minutes
Servings: 10 servings
Course: Dessert
Cuisine: American
Calories: 337
Ingredients Method Notes

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

Method
 

Cook the Rhubarb
  1. 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
  1. 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.
  2. In a small bowl, whisk together the 1 ½ cups spelt flour, 1 ½ teaspoons baking powder, and ¼ teaspoon fine sea salt.
  3. 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.
  4. Beat in the 1 egg and 1 teaspoon pure vanilla extract, mixing well to combine.
  5. 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.
  6. 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.
  7. 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.