Preheat oven to 350 degrees. Line a standard muffin pan with paper cupcake liners.

In a mixing bowl whisk together the flour, cocoa powder, baking soda, and salt.

In another mixing bowl whisk together the buttermilk, cola, grenadine, and vanilla and let sit until the cola stops fizzing.

In an electric mixer, preferably fitted with the paddle attachment, cream the butter and sugar together until light and fluffy, about 3 minutes. Add the egg and beat well. Turn the mixer to low and gradually add half the flour, then the buttermilk mixture, then the remaining flour. Using a rubber spatula, scrape the sides and bottom of the mixing bowl making sure all ingredients are combined. Divide the batter evenly into the prepared muffin tins and bake for 18 – 20 minutes or until a toothpick inserted into the center comes out clean. Let cool in the pan for 5 minutes then remove to a wire cooling rack to finish cooling.

Whip the cream with the powdered sugar and vanilla until soft peaks form.

Pipe the frosting onto the cooled cupcakes and top with a maraschino cherry.