Preheat oven to 350. Line two 12 cup muffin tins or silicone pans with cupcake liners.

Sift together the cake flour, baking powder, salt in medium bowl and set aside.

In smaller bowl mix food coloring, cocoa powder, to form thin paste without lumps. Set aside.

In large bowl beat butter and sugar together until light and fluffy. Beat in eggs one at a time then beat in vanilla and red cocoa paste.

Add one third of the flour mixture to butter mixture, beat well, beat in half of buttermilk.

Beat in another third of flour mixture, then second half of buttermilk.

End with last third of flour mixture, beat until well combined.

In small bowl mix vinegar and baking soda, add to cake batter and stir well.

Fill cups with batter a little under 3/4 full.

Bake approximately 20 minutes, rotating pans halfway through. Cupcakes are done when tops spring back up after patting.

Cool in tins 10 minutes, them cool completely before frosting.