01 - Preheat oven to 350°F. Grease and line two 8-inch cake pans with parchment paper.
02 - In a large bowl, whisk together flour, black cocoa, sugar, baking powder, baking soda, and salt until well combined.
03 - Add oil, milk, eggs, and vanilla to the dry mixture. Beat until fully incorporated. Stir in hot water until batter is smooth and thin.
04 - Divide batter evenly between prepared pans. Bake for 35–40 minutes until a toothpick inserted into the center comes out clean. Cool in pans for 10 minutes, then transfer to wire rack to cool completely.
05 - Combine cherries, sugar, and lemon juice in a saucepan. Simmer over medium heat for 5–7 minutes until cherries release juices. Whisk cornstarch with water, stir into cherries, and cook until thickened. Cool completely before using.
06 - Heat heavy cream until just simmering. Pour over chopped dark chocolate and black cocoa powder. Let stand for 3 minutes, then whisk until smooth and glossy. Add black food coloring gel for deeper color if desired.
07 - Place one cooled cake layer on serving plate. Carefully hollow out a shallow circular cavity in the center of the cake layer, about 2 inches deep and 4 inches wide, leaving border intact.
08 - Spoon cooled cherry compote into the hollowed cavity, mounding slightly. This creates the hidden bloody filling effect when cake is cut.
09 - Place second cake layer on top, pressing gently. Apply a thin crumb coat of ganache over entire cake, then chill for 15 minutes until set.
10 - Pour remaining black cocoa ganache over cake, using offset spatula to create smooth, glossy finish. Allow ganache to drip down sides naturally.
11 - Use red food coloring gel to draw vein-like patterns on cake surface. Create edible spiders with fondant or molded chocolate. Add edible glitter for spooky shimmer.