Upside Down Rhubarb Cake

Rhubarb is such a magical fruit, in season for a short time, it’s tart and fruity and adds the perfect flavor along with brown sugar and butter, to a simple vanilla cake for this Upside Down Rhubarb Cake.

When should you flip an upside down cake?

Most upside down cakes are fragile when still warm so they need to sit for at least 10 minutes before flipping. On the other hand you don’t want to wait too long as the fruit layer will get too attached to the pan. 10-15 minutes seems to be the ideal amount of time to wait before flipping an upside down cake.

What does Rhubarb taste like in a cake?

Rhubarb is naturally VERY tart; it releases quite a bit of moisture and becomes tender when cooked making it the perfect combo with a heftier vanilla cake. This cake has a brown sugar and butter base that the rhubarb is laid into which makes the rhubarb less tart and helps retain the moisture in the cake.

How do you remove an upside down cake?

There are a few ways to remove an upside down cake but my favorite is to use a parchment lined springform pan. This is the most foolproof way that I have found because you can gently remove the edges of the pan making sure nothing sticks. Then flip the cake over and carefully peel back the parchment paper.

Can you freeze an upside down cake?

Yes! I love to freeze this rhubarb cake by cutting any extra into individual slices, wrapping them in plastic wrap and then storing in a freezer ziploc bag. To defrost, take out as many slices as you want and defrost, still wrapped, in the fridge overnight or on the counter at room temperature for 4-6 hours.

Can I leave out the cornstarch?

Unfortunately, no. Cornstarch is necessary to absorb the extra moisture from the rhubarb. That being said, you can substitute the cornstarch with arrowroot starch instead!

Additional Recipes to try:

• Chocolate Raspberry Cake
• Plum Cake
• Aprikosenkuchen – Apricot Cake

Tips for making Upside Down Rhubarb Cake

• Young fresh rhubarb is best for this cake but frozen rhubarb will work as well. Ideally you still want the rhubarb to be stiff and not flopping.
• To create the mosaic design, do your best to cut all stalks the same length and pick stalks that are approximately the same width.
• In order for the cake batter to mix quickly and evenly, all ingredients need to be room temperature or slightly warm.
• Make sure the rhubarb is cut and tossed in starch before starting on the brown sugar base as it will start to firm up and won’t hold onto the rhubarb as well.
• Don’t underbake this cake, it should be a deep golden brown as much of the moisture from the rhubarb will soak into the cake which will keep it from drying out.

Ingredients

Rhubarb Layer

• Rhubarb: Rhubarb isn’t in season for long but when it is I can usually find it at the farmers market or Whole Foods. The stalks should be stiff not limp.
• Corn Starch: Starch is important because it absorbs and thickens the juices from the rhubarb that are released when rhubarb is cooked.
• Butter: Butter is used in both the bottom layer (which becomes the top) of the cake mixed with the brown sugar to create a delicious soak into the cake.
• Brown Sugar: This recipes uses light brown or standard brown sugar, it has a warm, caramel kind of flavor that mixes so well with the rhubarb.

Cake Layer

• All Purpose Flour: Any all purpose flour should work for this cake. I don’t recommend substituting other flours unless you are willing to do a little trial and error. I use King Arthur flour when baking.
• Baking Soda & Baking Powder: Both baking soda and baking powder leaven the cake and the baking soda also helps tenderize the cake.
• White Granulated sugar: Granulated sugar gets mixed with the other vanilla cake batter ingredients to sweeten the cake.
• Salt: a little salt balances out the sweetness and actually enhances the flavors!
• Eggs: I use standard large eggs from the grocery store, be sure they are at room temperature so they blend well into the other ingredients.
• Sour Cream: This cake is great because it’s pretty flexible, you can use sour cream but you can also use greek yogurt, skyr, or even quark in place of the sour cream.
• Butter: The butter for the cake batter should be soft before adding it into the cake but not melted.
• Vanilla and Almond extract: I like to use both extracts in this cake to give it a little extra depth of flavor but if needed you can leave out the almond extract.

How to make Rhubarb Cake

• Preheat the oven to 350º F and place a rack in the center of the oven.

Prepare the Rhubarb

• Rinse the rhubarb stalks and cut off both ends of each stalk.
• Cut the stalks into 2″ long sections. If needed, cut any extra wide stalks in half lengthwise so that they are all approximately the same width.
• Place the cut rhubarb into a medium mixing bowl and toss with the cornstarch until fully coated. Set aside.

Brown Sugar Butter Base

• Line a 9″ springform pan with a sheet of parchment paper. If using a leakproof style pan, lay the parchment across the bottom and then place the ring on top. This helps prevent leakage, it won’t stop it all together but definitely helps.
• In a medium pot or pan, add in the brown sugar and butter. Heat over medium low until melted and the it begins to bubble. Stir occasionally while cooking to prevent it from burning.
• Pour the brown sugar and butter mixture into the lined pan, tilt the pan so that the mixture reaches all the way to the edges.
• Arrange the rhubarb stalks on the brown sugar and butter base in your preferred mosaic pattern – they should cover the bottom of the pan with edges touching. I prefer to start in the center with two or three stalks parallel. Then switch and lay two or three perpendicular to the first ones you laid out.
• Continue this pattern around the center block until you reach the edges of the pan. Once you get close to the sides, you may need to trim the rhubarb pieces a little to get them to fit.
• Set aside while making the cake batter.

Vanilla Cake Batter & Bake

• In the bowl of a stand mixer, add in the flour, baking soda, baking powder, sugar, and salt. Whisk to combine and then add in the sour cream, butter, eggs, and vanilla and almond extracts.
• Beat with the paddle attachment, starting on low speed until just mixed and then increasing to high speed for another 30 seconds.
• Once mixed, scrape down the bottom and sides of the bowl to ensure all ingredients are fully mixed.
• Pour the batter over the rhubarb. Spread the vanilla cake batter over the rhubarb with a rubber spatula into a smooth layer all the way to the edges.
• Bake the cake for 25 minutes, then rotate the pan 180º and bake for another 15-20 minutes until the cake is a deep golden brown color and a toothpick inserted in the center of the cake comes out clean.
• Once baked, remove the cake from the oven and leave to cool on a rack for 10 minutes. Then, run a knife between the edge of the cake and the pan.
• Release the springform pan and remove the collar. Place a sheet of parchment paper over the cake, followed by a plate turned upside down that is larger than the cake.
• Holding onto the cooling rack and upside down plate, with the cake sandwiched in between, flip the whole sandwich over so the cooling rack is on top and the plate on the bottom. Do so carefully as some of the juices can spray a bit.

Cooling & Serving

• Remove the cooking rack and cake base. Gently peel the parchment away from the bottom of the cake. Allow to cool for at least another 10 minutes before cutting with a long sharp knife.
• Optionally serve with a drizzle of Vanille Soße. This cake is easier to cut once it is fully cooled but most delicious when warm.
• I recommend storing left overs in an airtight container in the fridge and then microwaving for 15-30 seconds before serving. And if you’re short on time but want a vanille soße dupe, melt down some vanilla bean ice cream and drizzle it on top instead!

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