Rainbow Cake (Six Layer Version)

I had these grandious plans to make a six layer coconut cake from the Peninsula G.rill, but that plan fizzled quickly when I got back home from running my half marathon and realized I was too tired and my cupboards were to bare to have even a semblance of what was needed for this monster cake. Another recipe for another time, I guess. I then thought I'd make a coconut layer cake that wasn't quite such a monster but decided that I really needed to go with something that I knew and was familiar with. Hence, the six layer rainbow cake that you see pictured above. This was my first time actually making it as a true six layer cake. My other versions involved a single layer and cupcakes so this was a deviation from the past, and even though I knew I had made something somewhat similar before, the ladies to whom I fed it to had not seen it before.

I followed the recipe exactly. It was helpful to have the wax paper under the layers of finished cake until I was finished icing. If not, can you imagine how messy that glass cake stand would have been? That's the first time I've actually used that method to frost a cake so it was fun to try a new technique.

Whipping up the buttercream frosting was an interesting experience. I thought for sure that I had whipped it too much and it had curdled, but lo and behold I waited just a few more minutes until the sound of the mixer changed and when I looked it was absolutely perfect. Not the smoothest buttercream you've ever seen but it was definitely tasty! Enjoy!

Rainbow Cake
Source: Whisk Kid

Cake:
3 cups cake flour
4 teaspoons baking powder
1/2 teaspoon salt
2-1/3 cup sugar
1 cup unsalted butter, room temperature
5 egg whites, room temperature
2 teaspoons vanilla
1-1/2 cups milk, warmed about 30 seconds in microwave to bring to room temperature
food coloring (gels work the best)

Preheat oven to 350 degrees. Oil and line three 9" cake pans or however many you have. (I just reused the three I had.)

Sift together the flour, baking powder, and salt. Set aside.

Cream the sugar and butter. Add the egg whites one at a time; add the vanilla and mix until fully incorporated. Then, alternating between wet and dry, add the milk and flour mixture in two parts.

Divide the batter between 6 bowls. (Easiest way is to do it by weight.) Stir in a fair amount of the appropriate food color to each bowl. Pour into pans and smooth out so batter is even. Bake for about 15 minutes each.

Remove from oven; let rest in pan on cooling rack for 10 minutes. Then flip, cover, and put them in the fridge to cool quickly.

Lemon Swiss Meringue Buttercream
To fill and crumb coat
9 egg whites
1-3/4 cup sugar
2 cups unsalted butter, room temperature
2 teaspoons lemon extract

To frost:
5 egg whites
1 cup sugar
1 cup butter, cubed, room temperature
1 teaspoon lemon extract

Cook the egg whites and sugar in a small saucepan over medium heat, whisking constantly, until the sugar is completely dissolved. Pour into another bowl and whip on high speed until room temperature (about 10 minutes). Then, on a medium-low speed, add the butter one cube at a time, waiting until each piece is incorporated before adding the next. After all the butter has been added, turn the mixer back up to high speed and whip until it has come together (about 5 minutes). Add the extract, beat briefly. (If the buttercream seems soupy after all the butter has been added, refrigerate for 5 to 7 minutes and continue whipping until it becomes fluffy and workable.)

Assembling:
Start with whichever end of the rainbow you would like to. Lay first layer down on plate. (I divided my frosting for filling and crumb coating into six bowls because I wanted to make sure I had enough.) Cover with layer of frosting, top with next cake layer, repeat for all layers. You may want to chill the cake at this point so the frosting is more workable. Cover the top and sides of the cake with frosting.