Preheat oven to 350°F (175°C). Liberally spray a solid 9-inch round cake pan with non-stick spray, line the bottom with a circle of parchment paper, and spray the paper as well.

In a small saucepan, melt the 4 tbsp of butter over medium heat. Whisk in the brown sugar until smooth. Pour this mixture evenly over the bottom of the prepared cake pan.

Arrange the pitted cherries in a tight, single layer on top of the brown sugar mixture in the pan. Set aside.

In a large bowl, whisk together the flour, granulated sugar, cocoa powder, baking soda, baking powder, and salt until well combined.

In a separate medium bowl, whisk together the eggs, buttermilk, vegetable oil, and vanilla extract.

Pour the wet ingredients into the dry ingredients and gently whisk until just combined. The batter will be thick.

Carefully pour the hot coffee (or hot water) into the batter. Whisk gently until the liquid is fully incorporated and the batter is thin and smooth.

Pour the chocolate batter slowly and evenly over the cherries in the cake pan.

Bake for 40-50 minutes, or until a toothpick inserted into the center of the cake comes out clean or with a few moist crumbs attached.

Remove the cake from the oven and let it rest in the pan on a cooling rack for exactly 15 minutes. Run a butter knife around the edges of the pan.

Place a serving platter upside down over the pan. Using oven mitts, quickly and confidently flip the pan and platter together. Gently lift the pan away and carefully peel off the parchment paper. Serve warm or at room temperature.