High Altitude Rainbow Birthday Cake
Soft and moist vanilla cake, baked in 6 rainbow colors, and frosted with fluffy sprinkle buttercream.
All recipes on Curly Girl Kitchen are developed for high altitude at 5,280 feet. See FAQs for adjusting to higher or lower elevations.
Equipment
- Six 6-inch cake pans
- Stand Mixer with Whisk Attachment
Ingredients
Cake
- 2 ⅓ cups cake flour, spooned and leveled
- 1 cup granulated sugar
- 2 tsp baking powder
- ½ tsp coarse Kosher salt (if using table salt, use half the amount)
- 2 large eggs
- 1 large egg white
- 1 cup whole buttermilk
- ⅓ cup unsalted butter, melted
- ⅓ cup vegetable oil
- 1 ½ tsp vanilla extract
- gel food coloring: red, orange, yellow, green, blue and purple
Buttercream
- 2 cups unsalted butter, softened to room temperature
- 4 cups powdered sugar
- 1 tbsp meringue powder
- 2 tsp vanilla extract
- ⅛ - ¼ tsp coarse Kosher salt (if using table salt, use half the amount)
- 2 tbsp sprinkles (nonpareils or confetti sprinkles)
- Lucky Charms marshmallows
Instructions
Cake
- Preheat the oven to 350F and spray the bottoms of six 6-inch cake pans with non-stick spray.
- In a large bowl, sift together the flour, sugar, baking powder and salt. Whisk to combine well.
- In another large bowl, whisk together the eggs, egg whites, buttermilk, melted butter, oil and vanilla extract until smooth.
- Add the dry ingredients to the wet, and whisk until mostly combined and smooth, about 10-15 seconds. Don't over-mix, since you'll be mixing the batter again when you add the food coloring.
- Divide the batter evenly between 6 small bowls. Tint each bowl of batter separately with red, orange, yellow, green, blue and purple gel food coloring. Use 1-2 drops for more vivid colors, or use a toothpick to add just a tiny bit of color for pastel shades. Stir the coloring into the batter until combined.
- Scrape the 6 colors of batter into the prepared pans. Bake on the center oven rack for about 13-15 minutes, until the centers spring back when lightly touched. Since there's a small amount of batter in each pan, the layers will be fairly thin.
- Cool the cakes in the pans before assembling and frosting.
Buttercream
- In the bowl of your stand mixer fitted with the whisk attachment, beat the butter for 1 minute until smooth.
- With the mixer running on low, add the powdered sugar by spoonfuls, the meringue powder and the salt, mixing until thick and combined.
- Add the vanilla and the milk; increase speed to medium and whip for 4-5 minutes, scraping the bowl down several times, until light and fluffy.
Assembly
- Remove the cooled cakes from the pans.
- Set the purple cake on a cake board. Frost with a thin layer of buttercream. Repeat stacking and filling with the remaining colors, ending with red on top.
- Frost the cake all over with a thin crumb coat of buttercream, and chill for 30 minutes.
- Fold the sprinkles into the remaining buttercream, and frost the cake all over with a final coat of buttercream.
- Fit a piping bag with tip 2M, and fill with the leftover buttercream. Pipe the buttercream in decorative peaks on top of the cake.
- Decorate with sprinkles and Lucky Charms marshmallows.
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