Strawberry Sheet Cake with Rhubarb Frosting
I am pretty darn pumped that it is officially rhubarb season. My rhubarb is HUGE! So big that I am reluctant to cut into it. Ha- just kidding! I can’t wait to chop those stalks down. Really though, I am waiting for strawberry season to hit so I can make the beloved flavor combination of strawberry rhubarb. I always hold my breath, just hoping my rhubarb will make it through to strawberry season since they are so far apart. In the meantime, while I impatiently wait for local strawberries, I like to cut away at the smaller stalks of rhubarb for different treats. And I’ll occasionally indulge in the strawberries that are coming from the south to make desserts, such as this cake. It’s hard to resist fresh fruit when it starts to pile up for reasonable prices in the grocery store. So finally, that brings me to this cake. About damn time!
Sooo this cake I made on a whim, for no special occasion, a few weeks ago. I generally don’t make cake for the heck of it, mostly because I don’t actually like cake… eeek!! I made a cake for my son’s birthday and I had one piece when we celebrated, but then I let everyone else eat it over the following days. I don’t know, I just really don’t enjoy all the buttery frosting, or even really the taste of cake. I am super weird like that. Unless it’s one of my favorite Milk Bar method cakes, where the actual cake part is minimal and the filings are at maximum. Bearing that in mind, I don’t mind sheet cake. I know, I know, it’s the same darn thing- but only kind of! I suppose there is sort of a less ratio of cake/frosting thing going on. The cake slices are usually more manageable and I don’t walk away with that heavy feeling in my stomach of ugh, I shouldn’t have eaten all that cake. But enough about me, let’s talk about this cake!
So this cake has lovely subtle flavors going on here. Neither the cake nor the frosting are particularly overpowering, which I love. One doesn’t cancel out the other. The cake is wonderfully moist thanks to the strawberry purée, and not overly sweet. The rhubarb meringue frosting is like eating a cross between whipped butter and heavy cream. But without the heaviness. The roasted rhubarb gives it a lovely hue and flavor. And then of course sprinkles! Who can resist cute little rainbow sprinkles when they are dotted over a cake? I know I can’t. Or jimmies? What do you call them? This cake stores beautifully in the refrigerator for a few days, if it can last that long after you’ve had one piece! Just know that the frosting does not retain its fluffiness after a night in the fridge. But that doesn’t make it any less delicious. Get scrounging in your garden, local farmers market or grocery store for the best looking fruit and get baking!
Strawberry Sheet Cake with Rhubarb Frosting
Yield: 16-20 slices
For the roasted strawberries and rhubarb
2 cups hulled and sliced strawberries
1/4 cup white granulated sugar, divided
1 cup diced rhubarb, from 4 to 5 small stalks
3 drops of red food coloring, optional
For the cake
2 3/4 cups cake flour, plus more for dusting pans
2 1/2 teaspoons baking powder
1 teaspoon salt
1 cup unsalted butter, at room temperature
1 3/4 cups granulated sugar
~1/4 cup whole milk
3 large eggs
2 teaspoons vanilla extract
For the rhubarb Swiss meringue frosting
3 large egg whites
3/4 cup white granulated sugar
1 cup unsalted butter, at room temperature, cut into 16 Tablespoons
1/4 cup rhubarb puree
2 to 3 drops of red food coloring, optional
To make the roasted strawberries and rhubarb, preheat the oven to 350ºF. Line a large baking sheet with parchment paper. Place the sliced strawberries on one side of the baking sheet and the diced rhubarb on the other side. Sprinkle half of the sugar over the strawberries and the remaining half of the sugar over the rhubarb. Gently toss. Place in the oven and roast the fruit for 10 minutes. Remove from the oven, while maintaining the oven temperature, and let cool for 5-10 minutes.
Add the strawberries to a blender or food processor and pulse until smooth. If you want the cake to be pink, add a few drops of red food coloring to the strawberries. Remove the strawberries and place in a large glass measuring cup. Rinse out the blender and add the rhubarb. Pulse until smooth. Pour into a separate glass measuring cup and set aside until ready to use.
To make the cake, grease a 9x13-inch baking pan and dust with flour, knocking out any excess.
In a medium mixing bowl, whisk together the cake flour, baking powder and salt. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, beat together the butter and sugar on medium-high speed until light and fluffy, about 4 minutes. In the glass measuring cup with the strawberry purée, pour in the milk until the level reaches 1 1/4 cups. Whisk the eggs and vanilla extract into the strawberry/milk mixture.
Reduce the mixer speed to low and, alternating between the dry ingredients and the strawberry mixture, add the them butter mixture just until combined. Pour the batter into the prepared baking pan, smoothing the top.
Transfer to the preheated oven and bake for 25-35 minutes, or until a toothpick inserted into the center comes out clean. Remove from the oven and let cool for about 10 minutes before inverting the cake on a cooling rack to let cool completely.
While the cake cools, make the frosting. Have ready a clean bowl in the stand mixer fitted with the whisk attachment. Make a double boiler by bringing a couple inches of water to a simmer in a medium saucepan. Place a heatproof bowl over the water fitted with a candy thermometer, making sure the bowl is not in the water, and add the egg whites and sugar, whisking to combine. Heat the mixture until it reaches 160ºF, whisking constantly.
Once the mixture has reached temperature, carefully pour the mixture into the prepared stand mixer bowl and turn the mixer on to high. Beat until fluffy and stiff peaks have formed, about 5-8 minutes. With the mixer running on low speed, add the butter, one cube at a time until smooth and glossy. Then, mix in the rhubarb purée and a few drops of red food coloring (if using), and beat until fluffy again. (Don’t worry if it becomes curdled, just keep mixing!)
Place the cake on a serving platter. Spread the frosting evenly over the cake. Garnish with sprinkles, if desired and serve immediately. Store any leftovers, well wrapped, in the refrigerator up to 5 days.
Source: Adapted from A Cozy Kitchen