Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.
In a medium bowl, sift together the flour, sugar, baking soda, salt, and cocoa powder.
In a large bowl, whisk together the vegetable oil, buttermilk, eggs, purple food coloring, vinegar, and vanilla until smooth.
Gradually mix the dry ingredients into the wet mixture, stirring until the batter is smooth and well combined.
Divide the batter evenly between the prepared pans and bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean.
Allow the cakes to cool in the pans for 10 minutes before transferring them to a wire rack to cool completely.
For the frosting, beat the cream cheese, butter, and vanilla extract together until smooth and creamy. Gradually add the confectioners’ sugar, beating until the frosting is fluffy and spreadable.
Once the cakes are completely cooled, spread a layer of frosting on top of one cake layer. Place the second layer on top and frost the top and sides of the cake as desired.