Ingredients:
- 2 1/2 cups (300g) all-purpose flour, plus more for dusting pans
- 2 1/2 teaspoons baking powder
- 1/2 teaspoon baking soda
- 1 teaspoon salt
- 1 cup (227g) unsalted butter, softened
- 2 cups (400g) granulated sugar
- 4 large eggs, at room temperature
- 1 tablespoon pure vanilla extract
- 1 1/4 cups (300ml) buttermilk, at room temperature
- Gel food colourings (red, orange, yellow, green, blue, purple)
- 1 cup (227g) unsalted butter, softened
- 4 cups (480g) powdered sugar, sifted
- 1/4 cup (60ml) heavy cream
- 2 teaspoons pure vanilla extract
- Pinch of salt
- Rainbow sprinkles, edible glitter
Instructions:
- Grease, flour, and line the cake pans with parchment paper.
- Whisk together flour, baking powder, baking soda, and salt in a bowl.
- Cream softened butter and sugar together until light and fluffy.
- Beat in eggs one at a time, then stir in vanilla extract.
- Gradually add the dry ingredients to the wet ingredients, alternating with the buttermilk, beginning and ending with the dry ingredients. Mix until just combined.
- Divide the batter evenly into six bowls. Tint each bowl with a different gel food colouring.
- Pour each coloured batter into a prepared cake pan and bake until a toothpick inserted into the centre comes out clean.
- Let the cakes cool in the pans for a few minutes, then invert them onto a wire rack to cool completely.
- Beat softened butter until smooth and creamy. Gradually add the powdered sugar, alternating with the heavy cream, until light and fluffy. Stir in vanilla extract and salt.
- Level the cake layers if needed (using a serrated knife). Place the first cake layer on a serving plate or cake stand. Spread with a layer of buttercream frosting. Repeat with the remaining cake layers, alternating colours.
- Frost the entire cake with the remaining buttercream frosting.
- Decorate with rainbow sprinkles, edible glitter, or other desired decorations.
- Refrigerate the assembled cake for at least 30 minutes to allow the frosting to set before serving.