Preheat the oven to 350 degrees and line a muffin pan with cupcake liners. Set aside.
Mix together flour, cocoa powder, baking soda, and salt in a bowl and set aside.
In a large mixing bowl, combine the sugar and butter beating on medium-high speed until light and creamy, about 3 minutes. Add the egg and beat for an additional minute. In a small bowl, combine the buttermilk, Coke, and vanilla extract. (Allow time for the foam to go go down when measuring the Coke, and your mixture might look curdled when you add the buttermilk. That's normal.)
Beginning with the flour mixture, add in small parts to the butter mixture, alternating with the Coke mixture. Beat each addition just until incorporated.
Divide the batter evenly between the muffins tins. Bake for 18-20 minutes, or until the tops spring back when touched lightly and a toothpick inserted in the center comes out clean. Cool and then transfer to a wire rack to cool completely.
Once cooled, use a paring knife to cut out a cone shape in the middle of each cupcake. Add a spoonful of cherry mixture (2 to 3 cherries) to the well.
Beat the heavy whipping cream in a chilled bowl with whisk attachment (or hand mixer), beginning on low speed. I like to place my mixing bowl and whisk attachment in the freezer for a few minutes before mixing. Once the cream gets frothy begin adding the powdered sugar, 1 tablespoon at a time, increasing speed as the cream comes together until you reach medium-high speed. Whip the cream until it holds stiff peaks (if you dip a spoon in it, the whipped cream should stay on the spoon when you turn it upside down). Pipe the whipped cream onto cupcakes as desired and top with maraschino cherries for garnish. Enjoy!