Ingredients:

  • 2.5 cups all-purpose flour
  • 1.5 cups granulated sugar
  • 1 tsp baking soda
  • 1 tsp salt
  • 0.75 cup unsalted butter, softened
  • 2 large eggs
  • 1 cup buttermilk, room temperature
  • 1 tsp white distilled vinegar
  • 1 tsp vanilla extract
  • 2 tsp royal purple gel food coloring
  • 1 cup unsalted butter, softened
  • 4 cups powdered sugar, sifted
  • 3 tbsp heavy cream
  • 2 tsp pure vanilla extract
  • 0.25 tsp salt

Instructions:

  1. Whisk together flour, sugar, baking soda, and salt to remove lumps and ensure even leavening.
  2. Beat the softened butter until pale and fluffy, then add eggs one at a time.
  3. Mix the purple gel coloring into the buttermilk and vinegar. Gradually stream this into the butter mixture, beating on low until the batter is a deep amethyst hue and smooth.
  4. Grease two 8-inch round cake pans and line the bottoms with parchment paper.
  5. Divide batter evenly between pans and bake at 350°F (175°C) for 28-32 minutes or until a toothpick inserted in the center comes out clean.
  6. Cool cakes in the pans for 10 minutes before transferring to a wire rack to cool completely.
  7. Beat butter until creamy, then gradually incorporate powdered sugar, heavy cream, vanilla, and salt. Whip on high for 3 minutes until silky with stiff peaks.
  8. Place one cake layer down, spread a thick coat of vanilla frosting, top with the second layer, and coat the exterior of the cake in a smooth finish.