Strawberry Cake with Rhubarb Swiss Buttercream

Sometimes, having this blog makes me feel like Dr. Jekyll  and Mr. Hyde. As my friends and family will tell you, I'm constantly on the quest for healthy and delicious tasting food. That's not to say an exquisite chocolate croissant won't catch my eye from time-to-time (*cough cough* Sub Rosa Bakery) but overall, eating well is one of my passions. It's not about counting calories - it's about nutrition. I  focus on gut-health, limiting the intake of processed foods, cruelty-free farms, and saying no to the usage of harmful pesticides. 

And yet.

This twinkling recipe from A Cozy Kitchen lured me. Hook, line, and sinker.

Now to be fair. It's not like we're talking about an individual eating an entire sheetcake by them-self. I had a much more manipulative strategy..... my loved ones! On a lazy Sunday afternoon, I invited everyone over for a potluck dinner and by chance... I just so happened to have this Strawberry Cake with Rhubarb Swiss Buttercream waiting for dessert. Pawns in my elaborate plot to eat a slice of cake. Moo ha ha ha.

I didn't add any food coloring so the light shade of pink is all-natural. Feel free to add a few drops if you want a more vibrant color. In addition, I used half the amount (two tablespoons) of sugar when roasting the fruits since they have their own sweetness. Neither the cake nor the frosting use the egg yolk so I recommend either buying a carton of egg whites or adding a bonus layer of rhubarb curd.

The cake itself is a white cake which produces a light crumb. The batter incorporates roasted strawberries which is a very light flavor. It doesn't scream strawberry but it's there and delightful. I love sheetcake because the ratio of cake to frosting is more balanced! 

The frosting was a bit of a hail Mary. I've made swiss buttercream so many times with my beloved version from Smitten Kitchen. This one, however, was not coming together and remained runny for a long time. Was the rhubarb still too warm? Oh crap! I was feeling defeated and texted my husband to pick up some heavy cream on his way home when I heard it - the slapping sound of frosting coming together. Yah - I know what it SOUNDS like >.< Don't lose faith - keep that mixer whipping. To up the citrus flavor, I folded in some lemon zest.

The cake was a hit with dinner guests. I still prefer the Rhubars and Rhubarb Chocolate Cake. Everyone liked that it was tart but not overpowering - perfect for the summer and those who appreciate a more subtle dessert. Pinkies up!

Strawberry Sheetcake with Rhubarb Meringue Frosting 

Roasted Strawberries + Rhubarb:
2 cups (from 1/2 pound) sliced strawberries
1/4 cup white granulated sugar, divided
1 cup diced rhubarb (from 4 to 5 shortish stalks)
3 drops of red food coloring (optional) 

Preheat the oven to 350 degrees F. Add the sliced strawberries to one side of a parchment-lined baking sheet and the diced rhubarb to the other side. Sprinkle about 2 tablespoons of sugar onto the strawberries and sprinkle the remaining 2 tablespoons of sugar onto the rhubarb. Toss them gently and keeping them separate, transfer them to the oven to roast for 10 minutes. 

Remove and allow them to cool for about 5 to 10 minutes. Add the strawberries to a blender and pulse until smooth. (You should end up with about 1/2 cup puree. Mix in 3 drops of food coloring, if you like.) Next, add the rhubarb to the blender and pulse until smooth.

Strawberry Sheet Cake:
2 3/4 cup cake flour, plus more for dusting pans
2 1/2 teaspoons baking powder
1 teaspoon salt
1 cups unsalted butter
1 3/4 cups white granulated sugar
3/4 cup milk
6 large egg whites
2 teaspoons pure vanilla extract or 1/4 teaspoon vanilla paste 

Keep the oven at 350 degrees F (as it was for roasting the strawberries). And grease a 13x9-inch baking pan. Set aside. 

In a medium bowl, add the cake flour, baking powder and salt. Whisk until combined. Set aside.
To the bowl of a stand-up mixer with the paddle attachment, add the butter and sugar. Beat until light and fluffy, about 2 to 3 minutes. In a measuring cup, pour in the milk, egg whites, vanilla extract or paste and reserved 1/2 cup strawberry puree (discard any extra) and whisk until combined. 

Turn the mixer to low speed and, alternating between the dry ingredients and the liquid ingredients (the strawberry/egg white mixture), add the them butter/sugar mixture until the batter is relatively smooth. 

Pour the batter into the prepared baking pan and transfer to the oven to bake for 25 minutes, until a skewer inserted into the center comes out clean.  Allow the cake to cool in the pan for about 5 minutes and then invert onto a cooling rack and cool to room temperature. It’ll probably take a good hour.

Rhubarb Swiss Meringue Frosting:
3 large egg whites
3/4 cup white granulated sugar
1 cup unsalted butter, at room temperature
1/4 cup rhubarb puree
2 to 3 drops of red food coloring (optional)

Bring a saucepan filled with a few inches of water. Place the clean bowl of a stand-up mixer atop the saucepan. Add the sugar and egg whites to the bowl and mix. Heat the mixture until it reaches 140 degrees F or until the sugar has dissolved completely. Carefully transfer the bowl to the stand-up mixer and with the whisk attachment, beat for 5 to 7 minutes, until very fluffy. Remove the whisk attachment and replace with the paddle attachment. With the mixer running on low speed, add the butter, one cube at a time until smooth and glossy. Lastly, pour in the rhubarb puree and red food coloring and mix until combined.