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 well combined.
03 - Add vegetable oil, milk, eggs, and vanilla extract to the dry mixture. Beat until fully incorporated.
04 - Stir in hot water until batter is smooth. Divide batter evenly between prepared pans. Bake for 35 to 40 minutes or until a toothpick inserted in center comes out clean. Cool 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, stir into cherry mixture, and cook until thickened. Let cool completely.
06 - Heat heavy cream in a small saucepan until just simmering. Pour hot cream over chopped dark chocolate and black cocoa powder in a heat-proof bowl. Let stand for 3 minutes, then whisk until smooth and glossy. Add black food coloring gel if deeper color is desired.
07 - Place one cooled cake layer on serving plate. Carefully carve out a shallow circle from center of cake layer, leaving at least 1-inch border on all sides.
08 - Spoon cooled cherry compote into the hollowed cavity. Place second cake layer on top, pressing gently.
09 - Spread black cocoa ganache evenly over top and sides of assembled cake. Refrigerate for 30 minutes or until ganache is set.
10 - Pipe or drizzle red food coloring gel in vein-like patterns over cake surface. Create spider shapes using fondant or melted chocolate. Add edible glitter or sprinkles as desired.