01 - Preheat oven to 350°F. Grease two 8-inch cake pans thoroughly with butter or oil, then line bottoms with parchment paper. Set aside while preparing batter.
02 - Sift together all-purpose flour, black cocoa powder, granulated sugar, baking powder, baking soda, and salt in a large mixing bowl. Whisk vigorously to ensure even distribution of leavening agents and cocoa.
03 - Create a well in center of dry ingredients. Add vegetable oil, whole milk, eggs, and vanilla extract. Beat with electric mixer on medium speed for 2 minutes until fully incorporated and smooth.
04 - Slowly pour in 1 cup hot water while mixing on low speed. Increase speed to medium and beat for 1 additional minute. Batter will appear thin—this is normal for achieving moist texture.
05 - Divide batter evenly between prepared pans. Bake at 350°F for 35-40 minutes until toothpick inserted into center emerges clean. Rotate pans halfway through baking for even rising. Cool in pans for 10 minutes, then transfer to wire rack.
06 - Combine pitted cherries, granulated sugar, and lemon juice in medium saucepan. Bring to simmer over medium heat. Cook for 5-7 minutes until cherries release juices and soften.
07 - Whisk cornstarch with 2 tablespoons water in small bowl until smooth. Stir into cherry mixture. Continue cooking for 2-3 minutes, stirring constantly, until compote thickens noticeably. Remove from heat and cool completely to room temperature.
08 - Heat heavy cream in small saucepan until just beginning to simmer—do not let it boil. Pour hot cream over finely chopped dark chocolate and black cocoa powder in heat-proof bowl. Let stand undisturbed for 3 minutes.
09 - Starting from center, whisk chocolate mixture in small circular motions gradually expanding outward until completely smooth and glossy. Add black food coloring gel drop by drop, whisking between additions, until desired darkness is achieved. Set aside to cool to spreading consistency.
10 - Once cakes are completely cooled, place one layer on serving plate. Using small serrated knife, carefully cut shallow circular depression in center of cake layer, leaving 1-inch border on all sides and 1-inch base intact.
11 - Spoon cooled cherry compote into hollowed cavity, filling just below surface level. Position second cake layer over filling, pressing gently to adhere. Refrigerate assembled cake for 15 minutes to stabilize before frosting.
12 - Spread cooled black cocoa ganache over top and sides of cake using offset palette knife. Create smooth, even finish or rustic textured appearance as desired. Chill entire cake for 20 minutes until ganache sets firm.
13 - Pipe red food coloring gel in radiating vein patterns across cake surface using small round tip or toothpick. Mold fondant or melted chocolate into spider shapes. Arrange spiders artistically on cake. Dust with edible glitter for dramatic effect.