Preheat oven to 350°. Generously butter two 9″ x 2″ round cake pans.  Dust with flour, and tap out the excess. Set aside. In a medium bowl, whisk together cake flour, salt, and cocoa. Set aside.

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

In a small bowl, whisk together the baking soda and vinegar. Add to the batter, and beat for 10 seconds. Evenly divide the batter between the prepared pans.

Place in oven and bake until a cake tester inserted in the center of each cake comes out clean, 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, top side up, to cool completely.

Make the frosting by creaming together the cream cheese and butter on medium-high speed for a minute or two, until well incorporated.  Beat in the powdered sugar until fluffy, then mix in the vanilla.

Using an offset spatula to frost the cake, spread 1-1/2 cups of the frosting on top of one of the cake layers. Place the second layer on top and spread the remaining frosting around the sides and top of the cake, swirling spatula as desired.

The cake can be stored, covered, in the refrigerator for up to 6 hours, or overnight. I like to serve the cake with a slight chill to it, since I like the cream cheese frosting to be a bit cool, with a thicker feel in the mouth. So I take the cake out of the fridge about 15 minutes prior to serving.