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.
Mix in the royal blue food coloring.
Next, add the buttermilk and vinegar and mix until combined.
Add the dry ingredients and mix on low until just combined. Finish mixing with a rubber spatula, scarping the bottom and sides of the bowl to make sure all the dry ingredients are mixed in.
Using a 1 tablespoon size scoop portion out the batter onto parchment lined baking sheets. You should have 18 cakes.
Bake for 8-9 minutes or until they spring back when lightly pressed.
Remove from the oven and place the pan on a rack to allow the cakes to cool completely.