01 - Preheat oven to 350°F. Grease and flour two 8-inch cake pans, then line bottoms with parchment paper.
02 - Sift together flour, black cocoa powder, sugar, baking powder, baking soda, and salt in a large mixing bowl.
03 - Whisk oil, milk, eggs, and vanilla extract into the dry mixture until fully incorporated.
04 - Gradually stir in hot water until batter achieves a smooth, thin consistency.
05 - Divide batter evenly between prepared pans. Bake for 35 to 40 minutes until a toothpick inserted in center comes out clean. Cool in pans for 10 minutes, then transfer to wire rack to cool completely.
06 - Combine cherries, sugar, and lemon juice in saucepan over medium heat. Simmer for 5 to 7 minutes until cherries release juices.
07 - Whisk cornstarch with water until smooth, then stir into cherry mixture. Continue cooking for 2 to 3 minutes until thickened. Cool completely before using.
08 - Heat heavy cream in small saucepan until just simmering. Remove from heat and pour over chopped dark chocolate and black cocoa powder in heat-proof bowl.
09 - Let mixture stand for 3 minutes, then whisk vigorously until glossy and smooth. Add black food coloring gel as needed for deeper color.
10 - Place one cooled cake layer on serving plate. Using a spoon, carefully hollow out a shallow circular well in the center, leaving border intact.
11 - Spoon cooled cherry compote into the cavity, creating the hidden surprise center.
12 - Position second cake layer over filled base. Press gently to secure.
13 - Pour black cocoa ganache over top and sides of cake, using offset spatula to create smooth, even finish. Refrigerate for 20 to 30 minutes until set.
14 - Use red food coloring gel to create vein-like patterns on cake surface. Shape spiders from fondant or melted chocolate and position as desired. Add edible glitter for final touch.