Rainbow Cake

I made a couple of rainbow cakes for a beloved teacher who retired after 32 years this year. We will miss you Mrs. Rogers.
I thought, oh this will be easy. 12 hours later I was finished. I did make 3 cakes, but it did take longer than I anticipated. I used the Rainbow Cake icing recipe from Martha Stewarts website found:
http://www.marthastewart.com/256688/rainbow-cake

but I used this recipe for the Cake:
Prepare cake mix as per package directions. In addition to this add,
 1 egg
1 cup flour
8 oz sour cream or Greek yogurt
 1 cup white sugar
1/3 tsp. salt
1 tsp. vanilla or other suited flavoring


 For the Filling and Crumb Coat

• • 9 large egg whites
  • 1 3/4 cups sugar
  • 2 cups (4 sticks) unsalted butter, cut into small pieces, room temperature
  • 2 teaspoons pure lemon extract

• For the Frosting

  • 5 large egg whites
  • 1 cup sugar
  • 1 cup (2 sticks) unsalted butter, cut into small pieces, room temperature
  • 1 teaspoon pure lemon extract

Directions

1. Make the filling and crumb coat: Cook egg whites and sugar in a small saucepan over medium heat, whisking constantly until sugar is completely dissolved. Transfer to the bowl of an electric mixer fitted with the whisk attachment; mix on high speed until mixture is room temperature. With the mixer on medium-low, add butter, one piece at a time, mixing well after each addition.
2. Remove whisk attachment and switch to paddle attachment. Increase speed to high and beat until buttercream comes together, about 5 minutes; beat in lemon extract.
3. Make the frosting: In a clean saucepan and bowl of an electric mixer, repeat process in step 1.

I don't eat sugar or flour (for recipes with no sugar and flour and see how I lost 74 lbs check out my blog justfortodaynosugarnoflour.blogspot.com
 Anyway, I didn't taste it, but my hubby loved the icing.  I do love icing that isn't made with powdered sugar. I didn't add the lemon, just vanilla.  I think I would try it again with almond next time.

Tips for making this cake:
 To make 3 cakes  I used 4 cake mixes with extender recipes.

To make the different colors I scooped out appx 2 cups batter in a large bowl and mixed gel food coloring in. I then baked them in 9 inch round pans for aprx 20 mins.  I let them cool and then cut them horizontally with a large serrated bread knife and  put them in the freezer for several hours to make icing easier.

Everyone at the retirement party loved the cake. I will take their word for it.