Heat the oven to 350°F. Grease two 8-inch round cake pans and line the bottoms with parchment.
Whisk the all-purpose flour, cocoa powder, granulated sugar, baking soda, baking powder, and fine salt together. Add the buttermilk, neutral oil, hot coffee, apple cider vinegar, and vanilla extract, then whisk just until the batter is smooth.
Divide the batter evenly between the pans and bake for 30 to 35 minutes until the centers spring back and a tester comes out with a few moist crumbs. Cool in the pans for 10 minutes, then turn the cakes out and cool completely.
Combine the sour cherries, cherry juice, granulated sugar, and cornstarch in a saucepan. Cook over medium heat for 4 to 6 minutes until glossy and thickened, then cool completely.
Beat the heavy cream, powdered sugar, and vanilla extract until firm peaks form. Keep the whipped cream chilled until assembly.
Place one cake layer on a serving plate and spread the cooled cherry filling over the top, leaving a 1/2-inch border. Spread about one third of the whipped cream over the cherries.
Add the second cake layer and cover the top and sides with the remaining whipped cream. Press most of the shaved dark chocolate onto the sides and scatter the rest over the top.
Pipe or spoon 12 small swirls of whipped cream around the top and add a whole cherry to each. Chill the cake for at least 1 hour before serving so the layers set cleanly.
