Moist Vanilla Rainbow Buttercream Cake
Moist Vanilla Rainbow Buttercream Cake is a vibrant, crowd-pleasing dessert that brings joy to any celebration. With its colorful layers and creamy frosting, this Colorful Celebration Cake is a must-make.
Ingredients
For the Cake:
- 3 ¾ cups 450g all-purpose flour
- 3 ½ tsp 14g baking powder
- 1 tsp 6g salt
- 2 ¼ cups 500g caster sugar
- 1 ¼ cups 282g unsalted butter, softened
- 4 large eggs plus 2 egg whites room temperature
- 1 ½ tbsp 22ml vanilla extract
- 1 ½ cups 320g buttermilk, room temperature
- Gel food coloring: ½ tsp red ¼ tsp each yellow, green, blue, purple, orange
For the Buttercream:
- 2 ½ cups 565g unsalted butter, softened
- 5 cups 500g powdered sugar
- 2 tsp 10ml vanilla extract
- 2 tbsp 30ml 2% milk
- Colorful sprinkles rainbow jimmies or nonpareils
Instructions
Prep Pans and Oven
- I preheat the oven to 350°F (175°C), butter six 8-inch cake pans, and line each with parchment paper. If fewer pans are available, I bake in batches.
Mix Dry and Wet Ingredients
- In a large bowl, I whisk 3 ¾ cups flour, 3 ½ tsp baking powder, and 1 tsp salt. In a separate bowl, I whisk 4 eggs, 2 egg whites, and 1 ½ tbsp vanilla. In a mixing bowl, I cream 1 ¼ cups butter and 2 ¼ cups caster sugar with a mixer on medium for 9–10 minutes until fluffy for Colorful Celebration Cake.
Combine Batter
- On low speed, I stream in the egg mixture, scraping the bowl. I alternate adding the dry mix and 1 ½ cups buttermilk, starting and ending with dry, mixing until just combined, scraping sides for Moist Vanilla Rainbow Buttercream Cake.
Color and Bake Layers
- I divide the batter into six bowls (about 1 ½ cups/280g each), adding red, yellow, green, blue, purple, and orange gel coloring to each. I spread each into a pan and bake for 17 minutes, until tops spring back. I cool in pans for 5 minutes, then transfer to a wire rack.
Make Buttercream
- I beat 2 ½ cups butter for 2 minutes until smooth, add 5 cups powdered sugar, and mix on low, then medium-high for 3–4 minutes. I add 2 tsp vanilla and 2 tbsp milk, mixing until fluffy.
Assemble and Frost
- I place the purple layer on a plate, spread ½ cup buttercream, and stack blue, green, yellow, orange, and red layers (upside down) with buttercream between each. I apply a thin crumb coat, chill for 15–20 minutes, then add a thick frosting layer, smoothing it out.
Decorate
- I pipe buttercream rosettes on the top edge with a star tip, add sprinkles along the bottom and top, and chill for 20–30 minutes before slicing with a hot knife.
Serve
- I bring Moist Vanilla Rainbow Buttercream Cake to room temperature for easy slicing and serve.