Make the batter. Sift the flour, sugar, baking soda, salt, and cocoa powder in a large bowl. This helps to aerate the dry ingredients and ensures a smooth batter. In another large bowl, use a handheld electric mixer to gently beat together the vegetable oil, buttermilk, eggs, red food coloring, vinegar, and vanilla extract until everything is well combined. Gradually add the sifted dry ingredients to the wet mixture in increments, beating on low speed until the batter is smooth and fully combined.