Preheat the oven to 350°F (175°C) and grease a 9-inch round cake pan with butter.

In a medium saucepan, melt 4 tablespoons of unsalted butter over medium heat. Stir in 1 cup of granulated sugar until dissolved, then add 2 cups of pitted tart cherries. Cook for about 5-7 minutes until syrupy.

Pour the cherry topping into the prepared pan, spreading it evenly.

In a large mixing bowl, sift together 1.5 cups of all-purpose flour, 1 cup of granulated sugar, 0.5 cup of unsweetened cocoa powder, 1.5 teaspoons of baking powder, 0.5 teaspoon of baking soda, and a pinch of salt.

In another bowl, whisk together 2 large eggs, 1 cup of buttermilk, 0.5 cup of vegetable oil, and 2 teaspoons of vanilla extract until smooth.

Gradually combine the wet ingredients with the dry mixture, stirring until just combined.

Carefully stir in 1 cup of boiling water to the batter until completely incorporated.

Pour the smooth cake batter over the caramelized cherry mixture in the pan and spread evenly with a spatula.

Bake for 35-40 minutes until a toothpick inserted comes out clean and edges pull away from the pan.

Let cake cool for about 10 minutes in the pan before inverting onto a platter.