Rhubarb Upside-Down Cake

Rhubarb upside-down cake is a simple and fuss-free dessert that anyone can make. The cake is soft and lightly spiced and you can make this with frozen rhubarb to enjoy a taste of spring any time of year!

Is anyone else SUPER excited for rhubarb season? I have five (count ‘em FIVE) rhubarb recipes I’m planning for this year, starting with this rhubarb upside-down cake.

Please note that I might postpone a few of those recipes until next year because I’m not sure everyone wants non-stop rhubarb recipes this spring. We’ll see :).

Anyway, this cake is an awesome way to celebrate one of the highlights of spring. It’s soft, moist, lightly spiced, and soooo yummy served warm with a big scoop of ice cream. PLEASE tell me you’ll try this one soon!

What is rhubarb?

If you’ve never had rhubarb before I’ll explain it a bit before diving into the instructions for make your rhubarb cake. 

Technically, rhubarb is a vegetable. (A vegetable is defined as anything that is the root, stem, or leaf of a plant.) Note that only the stalks of a rhubarb plant should be eaten; the leaves are poisonous.

Rhubarb looks a little like red celery and has a very sour taste on its own. You pretty much have to add some kind of sugar to rhubarb to make it edible.

While rhubarb is technically a vegetable, it’s legally a fruit.

In 1947 the U.S. Customs Court in Buffalo, NY, ruled that because rhubarb is typically used as a fruit (like in cakes and pies) it should be considered a fruit for tax purposes.

This meant rhubarb importers could pay less in tax since vegetables were taxed at a higher rate.

But however it’s classified, rhubarb is absolutely delicious. Rhubarb is hands-down one of my favorite fruits/veggies and I want everyone to love it the way I do!

And now, on to the recipe!

How to make your cake

• Beat butter and granulated sugar together until light and fluffy
• Beat in vanilla and eggs
• Then mix in your dry ingredients alternating with buttermilk

• Stir together butter, brown sugar, honey, and salt to form a paste 
• Pour into the bottom of a 9-inch round cake pan
• Arrange sliced rhubarb in a single layer on top of the paste
• Carefully pour the cake batter over the rhubarb

Then you’ll bake your cake for about an hour, invert onto a plate, and you’re ready to serve!

Notes:

• You’ll see in the recipe card that I added a little cardamom to my cake. Cardamom and rhubarb go together beautifully but if you don’t like cardamom or don’t have any you can omit it
• If you don’t have buttermilk you can substitute regular milk mixed with lemon juice or white vinegar
• As with all cake batters, take care not to over-mix this one. You’re done mixing when you no longer see big streaks of dry ingredients in the batter
• Your rhubarb should be in pieces about 1/4-inch thick
• I like to serve this cake with a big scoop of vanilla ice cream. Strawberry ice cream would also be a good choice since strawberry and rhubarb are a classic combination!
• Whipped cream is another delicious topping idea.

How to store your cake

Once your cake has cooled completely, cover it loosely with plastic wrap or a cake cover and it can be stored for a couple of days at room temperature. Be sure to let the cake cool completely before covering or the cake could sweat.

You can also store slices, tightly wrapped, in the freezer for about a month. Either defrost them at room temperature or pop them in the microwave (unwrapped) to hurry things along.

What can I substitute for buttermilk? Can I use regular milk?

If you don’t have buttermilk on hand you can substitute an equal amount of whole milk mixed with 1 1/2 teaspoons of white vinegar or lemon juice.

Regular milk on its own is not a substitute for buttermilk—buttermilk is more acidic than regular so adding lemon juice or vinegar to your milk is a necessary step.

A few more recipes you might enjoy
Blueberry Upside-Down Cake
Rhubarb Dump Cake
Strawberry Dump Cake
Blackberry Cheesecake

Did you make this rhubarb upside-down cake? That’s great! Let me know what you think with a comment and a rating below. Then post a pic on IG–tag @theitsybitsykitchen so I can see your delicious creations!

5 from 10 votes

Print

Rhubarb Upside-Down Cake

Prep Time

25 mins

Cook Time

55 mins

Total Time

1 hr 20 mins

 

Rhubarb upside-down cake is a simple but show-stopping dessert that's perfect for spring and summer!

Course: Dessert

Cuisine: American

Servings: 6

Author: Kelsie

Ingredients

Cake

• 12 tablespoons unsalted butter at room temperature
• 3/4 cup granulated sugar
• 2 teaspoons vanilla extract
• 2 large eggs
• 1 1/2 cups all-purpose flour
• 2 teaspoons baking powder
• 3/4 teaspoon salt
• 1/2 teaspoon ground cinnamon
• 1/8 teaspoon fresh ground cardamom optional
• 3/4 cup buttermilk*

Topping

• 5 tablespoons unsalted butter melted
• 2/3 cup packed light brown sugar
• 2 tablespoons honey
• 1/8 teaspoon salt
• 2 cups fresh or frozen sliced rhubarb**

Instructions

Cake

1. Preheat the oven to 350. Spray a 9-inch round cake pan with cooking spray.
2. Combine the butter and sugar in a large mixing bowl and beat on medium speed until light and fluffy, several minutes. Beat in the vanilla and eggs. Scrape down the sides and bottom of the bowl.
3. Whisk the flour, baking powder, salt, cinnamon, and cardamom (if using), together in a medium bowl. (These are your dry ingredients.)
4. With mixer on low, beat in half of the dry ingredients followed by half of the buttermilk until just incorporated. Scrape down the sides and bottom of the bowl.
5. Beat in the rest of your dry ingredients, then the rest of the buttermilk, again beating until just combined. (Your batter is fully mixed when you no longer see streaks of flour running through.)
6. Set the batter aside and make the topping.

Topping

1. Combine the butter, brown sugar, honey, and salt in a small bowl and stir together to form a paste. Spread into the bottom of the cake pan.
2. Arrange the rhubarb in a single layer in the bottom of the pan.
3. Carefully pour the cake batter over the rhubarb and use a small offset spatula to spread the batter out (gently!) if necessary.
4. Bake 55 to 70 minutes, until a toothpick inserted into the center of the cake comes out clean.
5. Cool the cake in the pan for 5 minutes, then run a knife around the edge of the pan a few times to loosen. Place a cake stand or large serving plate on top of the pan and flip.
6. If the cake sticks, turn the pan back to right side-up and run your knife around the cake a few more times and use a small offset spatula to lift the cake (again gently!) up. Then invert onto the serving plate again.
7. If any rhubarb sticks to the pan you can just pop it out with the spatula and replace the rhubarb where it should have been on top of the cake.
8. Cool for 20 to 30 minutes, then serve and enjoy.
9. Uneaten rhubarb upside-down cake can be stored at room temperature (covered) for up to 2 days. Be sure the cake is cooled completely to room temperature before you cover it.
10. Cake can also be stored in the freezer, tightly wrapped, for up to about a month.

Recipe Notes

• *You can substitute 3/4 cup whole milk mixed with 1 1/2 teaspoons of fresh lemon juice or white vinegar. Let the mixture sit for 5 minutes before using in the cake batter.
• **The rhubarb should be sliced about 1/4-inch thick. You’ll need about 7 to 8 ounces of rhubarb; you may need a little more or less than 2 cups sliced. Just use enough to cover the bottom of the pan.