Preheat the Oven: Preheat your oven to 350°F (175°C). Prepare two 9-inch round cake pans by greasing them lightly and dusting with flour. Set them aside.

Mix Dry Ingredients: In a medium bowl, whisk together the flour and cocoa powder until well combined.

Cream Butter and Sugar: In a large mixing bowl, beat the softened butter and granulated sugar with an electric mixer on medium speed for about 3 minutes, until light and fluffy.

Add Eggs and Vanilla: Add the eggs one at a time, beating well after each addition. Then mix in the vanilla extract.

Alternate Buttermilk and Dry Ingredients: Gradually add the flour mixture to the creamed butter, alternating with the buttermilk. Begin and end with the flour mixture. Stir just until combined—do not overmix.

Add Food Coloring: Add a dash of purple liquid food coloring to the batter. Stir gently until the color is evenly distributed, adjusting to your desired shade.

Incorporate Baking Soda and Vinegar: In a small bowl, mix the baking soda and vinegar. It will fizz slightly. Quickly fold this mixture into the batter for a light, airy texture.

Divide and Bake: Divide the batter evenly between the prepared cake pans. Use a spatula to level the tops. Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted in the center comes out clean.

Cool the Cakes: Allow the cakes to cool in the pans for 10 minutes. Then transfer them to a wire rack to cool completely before frosting.

Prepare the Frosting: In a large bowl, beat the softened cream cheese and butter together until smooth and creamy. Gradually add the powdered sugar, one cup at a time, beating until light and fluffy. Stir in the vanilla extract.

Assemble the Cake: Place one cake layer on a serving plate and spread a generous layer of frosting on top. Position the second cake layer over it and frost the top and sides evenly.

Decorate: Garnish with edible flowers, purple sugar sprinkles, or a dusting of cocoa powder for an elegant finish.