01 - Preheat oven to 350°F. Grease and line two 8-inch round cake pans with parchment paper.
02 - In a large bowl, whisk together flour, black cocoa powder, sugar, baking powder, baking soda, and salt until evenly combined.
03 - Add vegetable oil, milk, eggs, and vanilla extract to the dry mixture. Beat until well incorporated. Gradually stir in hot water until batter forms a smooth consistency.
04 - Divide batter evenly between prepared pans. Bake for 35 to 40 minutes until a toothpick inserted in center comes out clean. Cool layers completely in pans before removing.
05 - Combine pitted cherries, sugar, and lemon juice in a saucepan. Simmer over medium heat for 5 to 7 minutes until cherries release juices. Whisk cornstarch with water and stir into cherries. Continue cooking until mixture thickens. Cool completely before using.
06 - Heat heavy cream in a small saucepan until just simmering. Pour hot cream over chopped dark chocolate and black cocoa powder. Let sit for 3 minutes, then whisk until glossy and smooth. Add black food coloring gel if deeper color is desired.
07 - Place one cooled cake layer on serving plate. Use a spoon to carefully hollow out a shallow circular well in the center of the cake layer, leaving sides and bottom intact.
08 - Spoon cooled cherry compote into the hollowed cavity. Top with second cake layer, pressing gently to secure.
09 - Spread black cocoa ganache evenly over entire cake using an offset spatula. Refrigerate for 20 to 30 minutes until ganache sets completely.
10 - Pipe or drizzle red food coloring gel in vein-like patterns over cake surface. Create spider shapes from fondant or chocolate. Sprinkle with edible glitter if desired.