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Rainbow Cake

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This colorful layer cake from "Whisk Kid" blogger Kaitlin Flannery is ideal for a child's birthday party, or any time you want to make a big impression.

  • Yield: Makes one 9-inch-round six-layer cake

Ingredients

  • Vegetable shortening
  • 3 cups all-purpose flour
  • 4 teaspoons baking powder
  • 1/2 teaspoon salt
  • 2 sticks (1 cup) unsalted butter, room temperature
  • 2 1/3 cups sugar
  • 5 large egg whites, room temperature
  • 2 teaspoons pure vanilla extract
  • 1 1/2 cups milk, room temperature
  • Red, orange, yellow, green, blue, and purple gel food coloring
  • Lemony Swiss Meringue Buttercream Frosting

Directions

  1. Preheat oven to 350 degrees. Brush six 9-inch-round cake pans (or as many 9-inch cake pans as you have, reusing them as necessary) with shortening. Line bottom of each cake pan with parchment paper; brush again and set aside.

  2. In a large bowl, whisk together flour, baking powder and salt; set aside. In the bowl of an electric mixer fitted with the paddle attachment, cream together butter and sugar. Slowly add egg whites and mix until well combined. Add vanilla and mix until fully incorporated. Add flour mixture and milk in two alternating additions, beginning with the flour and ending with the milk. Mix until well combined.

  3. Divide batter evenly between six medium bowls. Add enough of each color of food coloring to each bowl, whisking, until desired shade is reached. Transfer each color to an individual cake pan. Transfer to oven and bake until a cake tester inserted into the center of each cake comes out clean, about 15 minutes (working in batches if necessary).

  4. Remove cakes from oven and transfer to a wire rack; let cool for 10 minutes. Invert cakes onto a wire rack; re-invert and let cool completely.

  5. Using a serrated knife, trim tops of cakes to make level. Place four strips of parchment paper around perimeter of a serving plate or lazy Susan. Place the purple layer on the cake plate. Spread a scant 1 cup buttercream filling over the first layer with a small offset spatula so it extends just beyond edges. Repeat process with blue, green, yellow, and orange layers.

  6. Place the remaining red layer on top, bottom-side up. Gently sweep away any loose crumbs with a pastry brush. Using an offset spatula, cover the top and sides with a thin layer of frosting (also use any of the excess frosting visible between the layers). Refrigerate until set, about 30 minutes.

  7. Using an offset spatula, cover cake again with remaining frosting.

Reviews Add a comment

  • chris.r.cornish
    10 MAR, 2017
    Awful recipe, not enough batter for a 9" tin Not worth the time. Great concept, just not worth it.
    Reply
    • darcydixon
      7 MAY, 2017
      Most layer cakes are made by filling the cake pan about 1/2 full, baking, then slicing the cake in half to make the "layers". Because this cake is 7 layers that are all different colors you need to initially make all the layers very thin. I've made this twice and both times it turned out perfectly. Just know that the batter will just barely fill the bottom of the pan with each layer.
  • Elroy_Jetson
    20 AUG, 2015
    You know what may make this a smidgen more awesome? Adding the appropriate color (and flavor) powdered jello for each color into the mix for flavor. Just a thought. Strawberry, Blueberry, Lemon, Lime, Orange...
    Reply
  • chhiwat
    15 AUG, 2015
    Good easy simple to learn thank you www.chefaicha.com
    Reply
  • Capricorn_noir
    10 JUL, 2015
    A couple of years ago I made a cake like this, however I colored each layer of icing and flavored each layer too according to color; for my granddaughter's birthday.
    Reply
  • MsSugaree
    20 JAN, 2014
    I made this for my friends birthday. It was a big hit, and everyone loved it. A bit time consuming, because I used two rounds pans. It was fairly easy to make.
    Reply
  • Sarah_Malta
    23 APR, 2013
    was watching the rainbow cake vid and i just want to share something with you. All you need to do to know the sequence of the rainbow colours is remember this sentence: Richard Of York Gave Battle In Vain. You take the first letter of each word R stands for red, O stands for orange and so on :) and voila you have the colours of the rainbow in sequence!! :) hope my suggestion proves futile when someone tries out the cake
    Reply
    • Elroy_Jetson
      20 AUG, 2015
      To remember the color sequence, to to bottom, we always remembered the name "Roy G. Biv". Red, Orange, Yellow (ROY) - Green (G.) - Blue, Indigo, Violet (BIV). There ya go.
  • satsiri
    13 MAR, 2013
    Awesome recipe. Works perfecty. Has become a new tradtion for celebrating St. Patrick's Day in my family!
    Reply
  • Nur Hadhira Halim
    17 FEB, 2013
    Ouhh my god! I love it!!! My No.#1 Cake :) #fingerlicking #loveit #loveumartha!!
    Reply
  • Sarah Price
    10 FEB, 2013
    I have made this twice now, my family loved it,the 1st I made the rainbow. The 2nd in honor of Valentine's day I made it just 2 layers in 2 shades of pink.. I bought salted butter oops,the buttercream came out very salty but I have had comments this is even better. Love this recipe!
    Reply
  • Apallas
    23 SEP, 2012
    Just wanted to say I made this same cake using gluten free boxed cake mix for my daughter's 4th birthday after having seen it on Pinterest. Came out perfect (as did the buttercream - I posted some buttercream tips on that page). The one thing I might do next time (which the Whisk Kid suggests on her video) is to actually weigh out the batter to ensure each layer is the same. Looked fine without doing that, but could have been even more 'perfect'. Cake was a MAJOR hit with kids and adults!
    Reply