Rhubarb Upside Down Cake

Light and fluffy hazelnut cake, baked with a layer of sugar roasted rhubarb this Rhubarb Upside Down cake is simple but so yummy! The sour cream whip dollop is also a game changer and works so well with both the rich nutty hazelnut and the tart rhubarb.

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 hazelnuts?

Unfortunately, no because the hazelnut flour is integral to the structure. That being said, you can use almond flour instead. OR just use this vanilla cake from the Yogurt Plum Cake recipe instead!

Additional Recipes to try:

• Raspberry Rhubarb Cream Scones
• Raspberry Almond Coffee Cake
• Raspberry Rhubarb Toaster Strudel

Tips for making 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 get that bright pink color you will need forced rhubarb but if you can only find late season, natural rhubarb that will still work and be beautiful!
• It’s best if you can let the rhubarb sit in sugar for an hour but I rarely have the time/patience to do so.
• In order for the cake batter to mix quickly and evenly, all ingredients need to be room temperature or slightly warm.
• Don’t underbake this cake, it should be golden brown because much of the moisture from the rhubarb will soak into the cake which will keep it from drying out.
• Be sure the sour cream and heavy cream are cold before you start whipping them.
• Store leftovers in an airtight container in the fridge or wrap individual slices in plastic and place in a ziploc bag in the freezer.

Ingredients

• 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. For the most vibrant pink rhubarb you’ll want to find forced rhubarb but any rhubarb will work and be delicious.
• White Granulated sugar: Granulated sugar coats the rhubarb to sweeten it and gets mixed with the other vanilla cake batter ingredients to sweeten the cake.
• Butter: The butter for the cake batter should be soft before adding it into the cake but not melted.
• Vanilla extract: Vanilla enhances the flavors and sweetness of the cake.
• Salt: A little fine sea 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.
• Hazelnut Flour: I love using hazelnut flour for this cake but almond flour (blanched or whole) will work too!
• All Purpose Flour: Any all purpose flour should work for this cake. I don’t recommend substituting with any other flours unless you are willing to do a little trial and error. I use King Arthur flour when baking.
• Baking Powder: Baking powder leavens the cake so make sure it hasn’t expired.
• Sour Cream: Sour Cream is one of my favorite additions to whipped cream because it adds just a slight tang but you can leave it out if you prefer or substitute it with cream cheese.
• Heavy Cream: Cold heavy cream is the base of the whipped cream topping, heavy cream or heavy whipping cream will work.

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 the stalks so that they fit into your metal pan and cover the bottom.
• Line a 9″ metal pan with a piece of parchment paper. Then grease the pan with soft butter before sprinkling 1 tablespoon of sugar across the bottom.
• Arrange the rhubarb across the bottom of the pan so it covers the surface. Sprinkle with another tablespoon of sugar and set aside.

Hazelnut Cake

• In the bowl of a stand mixer, add in the butter, sugar, salt, and vanilla extract.
• Use the paddle attachment to beat on medium high speed for 2 minutes until light and fluffy.
• Add in the eggs, one at a time, mixing completely before adding the next. Scrape the sides and bottom of the bowl in between each egg. After the first two eggs, add in the hazelnut flour and beat until just combined.
• Then continue with the remaining two eggs.
• Scrape the sides and bottom of the bowl again. 
• Pour in the all purpose flour and baking powder and mix again on medium speed for about 30 seconds until combined. 
• Pour the cake batter into the prepared pan and smooth out the top.
• Bake in the preheated oven for 30 minutes, then rotate 180 degrees and bake for another 20-25 minutes until golden brown and a toothpick inserted in the center, 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.

Sour Cream Whipped Cream

• In the bowl of a stand mixer, add in the heavy cream, vanilla, sugar, and salt. Use a whisk attachment to whip on medium high until just before stiff peaks form.
• Turn off the mixer and add in the sour cream. Turn the mixer back to medium high and whip until stiff peaks form.

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 dollop of the sour cream whipped cream.

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