6 tablespoons red food coloring or 1 teaspoon red gel food coloring dissolved in 6 tablespoons of water
1 1/2 teaspoons vanilla
1 1/4 cups buttermilk
2 teaspoons baking soda
2 1/2 teaspoons white vinegar
Equipment
electric mixer
9-inch round cake pans
parchment paper
Directions
Preheat oven to 350 degrees. 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.