Rainbow Cake with White Chocolate Buttercream

INGREDIENTS

• For Cake:
• 2 1/4 cups cake flour (9 ounces)
• 1 cup whole milk, at room temperature
• 6 large egg whites (3/4 cup), at room temperature
• 2 teaspoons almond extract
• 1 teaspoon vanilla extract
• 1 3/4 cups granulated sugar (12 1/4 ounces)
• 4 teaspoons baking powder
• 1 teaspoon table salt
• 12 tablespoons unsalted butter (1 1/2 sticks), softened but still cool
• Red, orange, yellow, green, blue, and purple gel food coloring
• For Frosting/Filling:
• 2 1/2 cups granulated sugar
• 10 large egg whites
• 2 pounds (8 sticks) unsalted butter, cut into tablespoons, softened
• 2 teaspoons pure vanilla extract
• 1 pound best-quality white chocolate, melted and cooled