Preheat the oven to 350°F (180°C). Spray two 9-inch cake pans with non-stick spray and line the bottoms with circles of parchment paper.
Mix the flour, sugar, baking soda, salt, and cocoa in a bowl and set aside.
Put the buttermilk, eggs, oil, vanilla, vinegar, and red food colouring in a bowl and mix on low for 2 minutes.
Slowly add the flour mixture to the buttermilk mixture. Mix until the lumps are gone, this should take 2-3 minutes.
Divide the batter evenly between your prepared cake pans.
Bake for 30 minutes or until a toothpick inserted into one of the cakes comes out clean.
Transfer to a wire cooling rack to cool completely before icing.