Vanilla Rainbow Layer Cake

Ingredients

For the White Vanilla Cake Layers:

• 3 cups (360g) cake flour, sifted
• 1 tbsp baking powder
• 1/2 tsp fine sea salt
• 1 cup (225g) unsalted butter, room temperature
• 2 cups (400g) granulated sugar
• 1 tbsp pure vanilla extract
• 1 cup (240ml) whole milk, room temperature
• 6 large egg whites, room temperature
• Gel food coloring: Red, Orange, Yellow, Green, Blue, and Purple

For the Fluffy Vanilla Buttercream:

• 2 cups (450g) unsalted butter, softened
• 7 cups (840g) powdered sugar, sifted
• 1/2 cup (120ml) heavy cream
• 1 tbsp pure vanilla extract
• Pinch of salt

Instruction

1.Prepare Oven & Pans:350°F (175°C) oven setup.

Preheat oven to 350°F (175°C). Line six 8-inch round cake pans with parchment paper and grease lightly (if you don’t have six pans, bake in batches).

2.Mix Dry & Wet Ingredients:

Whisk together cake flour, baking powder, and salt. In a separate bowl, cream butter and sugar for 4 minutes until pale and fluffy. Beat in the vanilla extract.

3.Alternate Milk & Flour:

On low speed, alternate adding the dry flour mixture and whole milk into the creamed butter, beginning and ending with dry ingredients.

4.Whip & Fold Egg Whites:Fold gently to preserve lightness.

In a clean bowl, whip the 6 egg whites until stiff peaks form. Gently fold the whipped egg whites into the batter until just combined.

5.Tint the 6 Batter Portions:Divide into 6 bowls (~1 cup per bowl).

Divide batter equally into 6 separate bowls. Add gel food coloring to each (red, orange, yellow, green, blue, purple) and mix gently until bright and uniform.

6.Bake & Cool:12 to 15 minutes per batch.

Spread each colored batter into a prepared pan. Bake for 12–15 minutes until set and a toothpick inserted in the center comes out clean. Cool completely on wire racks.

7.Whip Frosting & Assemble:Red layer on bottom, purple on top.

Beat butter for 2 minutes, then gradually blend in powdered sugar, heavy cream, vanilla, and salt on high speed until fluffy. Stack layers in reverse rainbow order (purple, blue, green, yellow, orange, red) with a layer of buttercream between each. Frost top and sides smooth with white buttercream.