Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans. In a large bowl, sift together the flour, cocoa powder, baking soda, baking powder, and salt. In another bowl, beat together the sugar, eggs, buttermilk, oil, and vanilla extract until smooth. Gradually mix in the dry ingredients, then stir in the hot water until fully combined.

Divide the batter evenly between the two prepared pans. Bake for 30–35 minutes, or until a toothpick inserted in the center comes out clean. Let cakes cool in the pans for 10 minutes, then transfer to wire racks to cool completely.

In a large bowl, beat the butter until creamy. Add the cocoa powder and mix until smooth. Gradually add powdered sugar, alternating with heavy cream, until you reach a thick, spreadable consistency. Mix in the vanilla extract.

Place one cake layer on a serving plate and spread with a generous amount of frosting. Add the second layer and frost the top and sides of the cake. Smooth the edges or leave it rustic — either way, it’ll taste amazing!