Preheat oven to 350° F. Grease and flour 3 (8-inch) cake pans. Set aside.
In a large bowl, cream together the butter and sugar until light and fluffy. Add eggs, one at a time, mixing just until the yolk disappears.
In a small bowl whisk together the red food coloring, cocoa, salt and vanilla until blended. Add the cocoa mixture to the creamed butter and sugar mixture. Blend on medium-low until combined, scraping down the sides of the bowl as needed.
Add ⅓ of the buttermilk and blend on low until incorporated. Next add ⅓ of the flour and mix on low. Scrape down the sides of the bowl as needed. Repeat by adding ½ of the remaining buttermilk and then ½ of the remaining cake flour taking care not to over-beat after each addition. Blend on low just until incorporated. Repeat until all the buttermilk and flour are incorporated.
In a small cup stir together the vinegar and baking soda, until completely dissolved. Using a rubber spatula, gently fold the vinegar mixture into the cake batter. Do not beat!
Divide the batter equally into the three prepared 8-inch cake pans and bake until a toothpick inserted in the center comes out clean (moist crumbs are okay - no wet batter) about 18 to 20 minutes. DO NOT OVER BAKE. Cool in the pans for 10 minutes, then turn the cakes out and cool completely on a wire rack.