Preheat oven to 350°F (175°C). Grease and line a rectangular sheet pan.
Whisk together flour, cocoa, sugar, baking soda, baking powder, and salt.
Add eggs, buttermilk, oil, and vanilla. Mix until smooth.
Slowly pour in the hot coffee and mix until combined. The batter will be fairly thin.
Pour into the pan and bake for 25–30 minutes, until a toothpick comes out with a few moist crumbs. Cool completely.
Add cherries, sugar, cornstarch, and lemon juice to a saucepan. Cook over medium heat until the cherries soften and the mixture thickens. Cool completely.
Whip heavy cream, powdered sugar, and vanilla until thick and fluffy.
Spread the cherry filling over the cooled chocolate cake.
Spread the whipped cream evenly over the cherries.
Heat the cream until hot, pour over chopped chocolate, wait 2 minutes, then stir until smooth. Add butter for extra shine.
Pour the ganache over the cream layer and gently spread it across the top.
Refrigerate for at least 2 hours before slicing.
Cut into squares and decorate with cherries and chocolate shavings.
