Preheat oven to 350°F. Prepare four 6-inch round baking pans by spraying with baking and lining with parchment paper. Or, use GOOP with parchment paper. (This will leave you with two extra cakes to freeze for later or snack on.)
In a 2 cup measuring cup (or medium bowl) pour the buttermilk. Add the vanilla, vinegar, and red food coloring to the buttermilk and whisk to fully combine. Set aside.
In a large bowl, add sugar, oil, and eggs and whisk together by hand until it is smooth and light yellow.
Add cake flour, cocoa, and baking powder to the sugar mixture and whisk until just combined.
Now add the buttermilk mixture and whisk until just combined. You do not want any lumps, but I do recommend being gentle with this batter.
Pour batter evenly into each pan and bake for 22-32 minutes. When using my convection oven I will bake these at 325°F for 22 minutes. The cake is done when it does not appear wet on the top and if you press your finger gently in the center of the cake it feels firm.
Allow to cool in the pan for about 5 minutes, then invert onto a cooling rack. Let cakes continue to cool until ready to assemble.