Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.
In a large mixing bowl, whisk together the flour, sugar, baking soda, baking powder, salt, and cocoa powder until well combined.
In another bowl, mix the vegetable oil, buttermilk, eggs, vanilla extract, and purple food coloring until smooth.
Gradually add the wet ingredients to the dry ingredients, mixing until just combined.
Carefully stir in the boiling water until the batter is smooth and well combined.
Divide the batter evenly between the prepared cake pans. Bake for 30-35 minutes, or until a toothpick inserted in the center comes out clean.
Allow the cakes to cool in the pans for 10 minutes before transferring them to wire racks to cool completely.
For the frosting, beat the cream cheese and butter together in a large bowl until creamy.
Gradually add the powdered sugar, mixing until smooth.
Stir in the melted white chocolate and vanilla extract until fully combined.
Once the cakes are completely cooled, place one layer on a serving plate and spread a generous amount of frosting on top.
Place the second layer on top and frost the top and sides of the cake.