Dry Ingredients: Start by sifting flour, baking powder, brown sugar, salt, cocoa powder into a large mixing bowl. Make sure to break apart all the clumps of the brown sugar.
Wet Ingredients: Mix buttermilk, egg, butter, vanilla extract, and food coloring until smooth.
Combine dry and wet ingredients until smooth.
Oil donut baking tray and put batter into a piping bag. Pipe the batter into the trays.
Bake at 350° for 10 minutes. Set aside and let fully cool down before glazing.