1. Heat the oven to 350 degrees. Generously butter two 9-by-2-inch round cake pans. Sprinkle with flour and tap out the excess. Set aside.
In a medium bowl, whisk cake flour, salt and cocoa together. Set aside.

2. In the bowl of an electric mixer fitted with the paddle attachment, combine the sugar and oil and beat on medium speed until well combined. Add the eggs, one at a time, beating will after each addition. Add the food coloring and vanilla and beat until will combined.
Add flour mixture, alternating with buttermilk, scraping the sides of the bowl with a rubber spatula as needed.

3. In a small bowl, mix baking soda and vinegar until combines. Add to the batter and beat for 10 seconds. Evenly divide the batter between the two prepared pans.

4. Bake until a cake tester inserted in the center of each cake comes out clean, about 30 to 35 minutes. Transfer to a wire rack to cool in the pans for 5 minutes. Remove from the pans and return to the rack to cool completely.

For the Frosting:

1. In a large bowl, combine the cream cheese and butter. Using an electric mixer set on medium-high speed, beat until smooth. Reduce the speed to low, add the confectioner's sugar and beat until smooth. Beat in the vanilla until well blended.

2. Use immediately or cover and refrigerate for up to 1 week. Bring to room temperature before using.