1. Make the Cupcakes: Preheat the oven to 350°F and line a standard muffin pan with paper liners; set aside.
2. Sift together flour, cocoa powder, baking soda, and salt in a small bowl and set aside.
3. In a mixing bowl, combine the sugar and butter and beat on medium-high until light and creamy, about 3 minutes. Add the egg and beating for an additional minute. In a large mixing cup or small bowl, combine the buttermilk, Coke and vanilla extract. (Make sure you wait for the foam to go down when measuring the Coke and don't worry if your mixture looks curdled when you add the buttermilk.)
4. Beginning with the flour mixture, add in 4 parts to the butter mixture, alternating with the Coke mixture. Beat each addition just until incorporated. Give the final mixture a good mix with a rubber spatula to make sure it is thoroughly combined.
5. 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 cupcake comes out clean. Cool for 5 minutes in the pan and then transfer to a wire rack to cool completely.
6. Fill the Cupcakes: 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.
7. Glaze the Cupcakes: In a small bowl whisk together the powdered sugar and coke. Let sit 5 to 10 minutes to thicken. It should drip off of a soon very slowly. Using a small offset spatula, drizzle a little of the glaze onto the middle of each cupcake and then gently spread it over the top.
8. Frost the Cupcakes: Beat the heavy whipping cream in a chilled bowl with whisk attachment (or hand mixer), beginning on low speed. 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.