01 - Preheat oven to 350°F. Grease two 8-inch cake pans and line with parchment paper.
02 - Whisk together flour, black cocoa, sugar, baking powder, baking soda, and salt in a large bowl.
03 - Add oil, milk, eggs, and vanilla to dry mixture. Mix until well combined, then stir in hot water until batter is smooth.
04 - Divide batter evenly between prepared pans. Bake for 35-40 minutes or until a toothpick inserted in center comes out clean. Cool completely.
05 - Combine cherries, sugar, and lemon juice in a saucepan. Simmer over medium heat for 5-7 minutes. Mix cornstarch with water, stir into cherries, and cook until thickened. Cool completely.
06 - Heat heavy cream until just simmering. Pour over chopped dark chocolate and black cocoa. Let sit for 3 minutes, then whisk until smooth. Add black food coloring if desired.
07 - Place one cooled cake layer on serving plate. Carefully hollow out a shallow circle in the center of the cake.
08 - Fill the cavity with cooled cherry compote. Place second cake layer on top.
09 - Spread black cocoa ganache evenly over entire cake. Refrigerate until ganache is set.
10 - Create decorative red vein patterns with red gel. Form edible spiders with fondant or chocolate. Add edible glitter or sprinkles as desired.