Preheat your oven to 350°F (175°C) and prepare two 8-inch round cake pans by spraying them with nonstick spray and placing parchment paper at the bottom.

In a large mixing bowl, sift together the all-purpose flour, black cocoa powder, granulated sugar, baking powder, baking soda, and salt. Set aside.

In a separate bowl, whisk together the buttermilk, canola oil, eggs, and vanilla extract until smooth.

Make a well in the center of the dry mixture, then pour in the wet ingredients and gently mix until just combined. Fold in the hot coffee carefully.

Divide the batter evenly between the prepared cake pans and bake for 30-33 minutes or until a toothpick comes out clean.

In a saucepan over medium heat, combine blackberries, sugar, lemon juice, zest, and optional cinnamon stick. Simmer until berries break down. Mix cornstarch with water and stir into the compote until thickened.

Beat together the cream cheese and unsalted butter until creamy. Gradually mix in the powdered sugar and black cocoa powder until fluffy.

Level the tops of the cooled cakes with a serrated knife, layer with blackberry compote, and frost with black cocoa buttercream.

Decorate with any remaining frosting, fresh blackberries, and chocolate skulls for a spooky presentation.