Preheat your oven to 350℉.
In a bowl whisk together the flour, baking powder, baking soda, kosher salt and cocoa. Set aside.
In a bowl using a hand mixer or in the bowl of a stand mixer, cream together the butter and granulated sugar for about 1-2 minutes.
Add the egg and vanilla and beat until thoroughly combined.
Next, add the buttermilk, vinegar and flour mixture and mix on low until justcombined.
Finish mixing with a rubber spatula, scarping the bottom and sides of the bowl to make sure all the dry ingredients are mixed in.
Divide the batter in half. Color one blue and the other red.
On a piece of plastic wrap place red batter in a like on the plastic wrap, next place the blue batter next to it.
Roll up in the plastic wrap and twist the ends.
Place the tube in a large pastry bag that has been fitted with a large round tip.
Draw 12 2" circles evenly spaced on the parchment paper. Place the paper in the pan with the drawn circles on the bottom.
Pipe the batter to fit inside the circles.
Place the pan in the freezer for 15 minutes.
Bake for 12-13 minutes, or until the top of the cakes spring back when lightly pressed. Start checking at 11 minutes. Do not over bake.