Preheat oven to 350°F
Place teaspoon of butter in each of 3 round 9-inch layer cake pans and place pans in oven for a few minutes until butter melts. Remove pans from oven, brush interior bottom and sides of each with butter and line bottoms with parchment.
Whisk cake flour, cocoa and salt in a bowl.
Place oil and sugar in bowl of an electric mixer and beat at medium speed until well-blended. Beat in eggs one at a time. With machine on low, very slowly add red food coloring. (Take care: it may splash.) Add vanilla. Add flour mixture alternately with buttermilk in two batches. Scrape down bowl and beat just long enough to combine.
Place baking soda in a small dish, stir in vinegar and add to batter with machine running. Beat for 10 seconds.
Divide batter among pans, place in oven and bake until a cake tester comes out clean, 40 to 45 minutes. Let cool in pans 20 minutes. Then remove from pans, flip layers over and peel off parchment. Cool completely before frosting.
Frosting: Place cream cheese and butter in a medium bowl. With a hand-held electric mixer, beat until light and fluffy, about 2 minutes. Add sugar and vanilla. Beat, on low speed to combine. If too soft, chill until slightly stiff, about 10 minutes, before using.