Preheat oven to 320°F (160°C). Prepare two 8-inch round cake pans.
Mix flour, sugar, cocoa powder, baking soda, baking powder, and salt. Add oil, buttermilk, hot water or coffee, eggs, and vanilla extract. Mix until smooth.
Pour batter into prepared pans and bake for 30-35 minutes, or until a toothpick comes out clean. Let cool in pans for 10 minutes, then transfer to a wire rack to cool completely.
In a small saucepan, combine 1/2 cup sugar, 1/2 cup water, and cherry liqueur. Bring to a boil, then reduce heat and simmer for 5 minutes. Let cool.
Split each cake layer in half horizontally. Brush each layer with the cherry syrup. Spread whipped cream and cherries on each layer, then stack them.
Frost the outside of the cake with the remaining whipped cream and sprinkle with powdered sugar. Top with dark chocolate shavings if desired.
Notes
For the best flavor, use high-quality dark chocolate and fresh cherries. The cake is best served chilled.