Preheat oven to 350ºF. Grease 2 9” round cake pans.
Mix flour, salt and cocoa powder in a medium sized bowl.
In a large bowl, cream butter and sugar until fluffy. Add eggs, beating well. Add vanilla and mix until incorporated.
In a small bowl mix buttermilk and food coloring.
Alternating between the two, add the flour mixture and the buttermilk mixture to the creamed butter mixture.
In a small bowl mix vinegar and baking soda. Let fizz and then incorporate into batter with a spatula, stirring just until combined.
Divide batter evenly between two cake pans.
Bake at 350ºF for 35-40 minutes, or until a toothpick inserted into the center comes out clean.
Let cool on a wire rack 10 minutes before removing from pan.
Notes
*Don't Have Buttermilk? Make your own buttermilk by putting 1 ½ tablespoon white vinegar in a liquid two cup measure and fill with regular milk to the 1 ½ cup mark. Let your buttermilk mixture stand for 5 minutes before using in the recipe.