Rainbow Marble Layer Cake
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Serves: 1, 8-inch, layer cake
 
A festive cake with rainbow marbled vanilla bean + buttermilk cake layers frosted with swirls of silky vanilla bean swiss meringue buttercream.
Ingredients
  • 3 ¾ cups AP flour
  • 1 teaspoon baking powder
  • ½ teaspoon soda
  • ¾ teaspoon Kosher salt
  • 3 sticks unsalted butter, softened
  • 2 ¼ cups sugar
  • 2 vanilla beans (or 1 tablespoon extract)
  • 1 cup buttermilk
  • 3 eggs plus 1 yolk
  • Gel food coloring plus 1 tablespoons of buttermilk or milk for each color
Instructions
  1. Preheat the oven to 350°F. Line and spray 3, 8-inch, cake pans.
  2. Whisk flour, baking powder, baking soda, and salt in a mixing bowl. Set aside.
  3. In the bowl of a mixer, beat the butter until smooth and creamy. Beat in the sugar and the insides of the vanilla beans (or extract), mix for 2-3 minutes until pale and fluffy. Beat in the eggs, one at a time, mixing well after each addition and scraping the bowl as needed. Next, beat in ⅓ of the flour mixture, followed by half of the buttermilk, and repeat ending with the flour mixture until just incorporated. Separate the batter into bowls (the number depending on how many colors you are using). Mix each gel color with 1 tablespoon of buttermilk or milk, fold one color into each bowl of batter. Divide the batters between each cake pan, making sure there are scoops of each color of batter in each pan, using a skewer or butter knife, swirl the batter a few times in each pan. Smooth the tops as best as you can and tap each pan on the counter a few times to even out the surface of the batter and release any large bubbles. Bake for 25 minutes or until the cakes spring back to the touch and a toothpick inserted in the center comes out clean. Cool completely on a wire rack before frosting.
  4. To frost the cake:
  5. Spread a tablespoon of frosting onto a cake board or cake plate and place the bottom cake layer on top--this will keep the cake in place and prevent sliding. Spread about ½ cup of frosting over the first layer, stacking the second layer on top and repeat. Once the cake is filled and stacked, spread a thin layer of frosting over the entire cake--this is the crumb coat, it's a thin layer of frosting that catches the loose crumbs and prevents them from getting into the final coating of frosting. Smooth out the crumb coat as much as possible and refrigerate until firm--at least 1 hour. Use the remaining frosting to give the cake a final decorative layer of icing.
Notes
The marble effect looks best when you use between 2 and 4 colors, otherwise, it just looks a little muddy.

I used whole vanilla beans in this recipe, though you can use extract or paste (about 1 tablespoon in the cake and 2 teaspoons for the frosting). When I buy vanilla beans, I store them upright in a lidded jar with about ½ inch of clear, flavorless alcohol (like vodka). This keeps the beans from drying out and when it comes time to use one, instead of splitting & scraping, I just snip off one end squeeze all the way down from the other end and into my recipe. Then I pop the pod into a jar of sugar or alcohol (for extract).

I used 8-inch round cake pans with 3-inch sides for this recipe.

This amount of batter also makes a 3-layer, 6-inch, cake plus 12 cupcakes.

For the sprinkles, I used Sweetapolita Carousel Sprinkle Medley and clear sanding sugar.
Recipe by hungrygirlporvida.com at http://www.hungrygirlporvida.com/blog/2016/08/10/rainbow-marble-layer-cake/