Preheat oven to 350 degrees. Grease and flour three 9-inch round layer cake pans. Line with a parchment circle (on top of the flour) if you desire.
In the bowl of an electric mixer with the paddle attachment, beat the sugar and eggs together until well combined.
Sift the flour, baking soda, salt and cocoa powder together, and set aside.
In a separate bowl (or liquid measuring cup), mix together oil, vinegar, food coloring and vanilla. Add to the eggs and sugar, and beat until combined.
Starting and ending with the flour mixture, alternate adding the flour mixture and the buttermilk to the wet ingredients.
Let your batter rest for 30 minutes before baking.
Pour batter into your prepared pans. Tap them on the table to level out the batter and release any air bubbles. Bake for 25 minutes or until a cake tester inserted near the middle comes out clean. Be careful not to overbake, or you will have a dry cake.
Set the layers cool on a wire rack for about 10 minutes before turning out of their pans. Cool completely before frosting.