In a large bowl, whisk together flour, cocoa powder, brown sugar, salt, and baking powder.
In a medium bowl, whisk together buttermilk, melted butter, vanilla, eggs, and food color.
Add the wet ingredients to the dry ingredients, and stir until just combined. Do not overmix.
Lightly grease regular-sized donut pans, or heart-shaped, if you have them!
Pour the batter into a gallon-sized plastic bag, and snip the corner.
Pipe the batter into the donut cavities, filling them about 2/3-full.
Bake at 350 degrees for 10-12 minutes, or until donuts spring back when lightly pressed.
Remove to wire racks to cool completely.
Meanwhile, prepare icing.