01 - Preheat oven to 350°F. Generously grease two 8-inch round cake pans with butter or cooking spray, then line bottoms with parchment paper circles.
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.
03 - Create a well in center of dry ingredients. Pour in vegetable oil, whole milk, cracked eggs, and vanilla extract. Beat with electric mixer on medium speed until fully incorporated.
04 - Slowly stream in 1 cup hot water while mixer runs on low speed. Increase to medium and beat for 2 minutes until batter transforms into silky smooth consistency.
05 - Divide batter evenly between prepared pans. Bake at 350°F for 35-40 minutes until wooden skewer inserted into center emerges clean. Cool in pans 10 minutes, then turn out onto wire rack to cool completely.
06 - Combine pitted cherries, granulated sugar, and lemon juice in medium saucepan. Bring to simmer over medium heat, stirring occasionally. Cook for 5-7 minutes until cherries release juices.
07 - Whisk cornstarch with 2 tablespoons water in small bowl until smooth. Stir slurry into simmering cherry mixture. Continue cooking 2-3 minutes until compote thickens noticeably. Transfer to bowl and refrigerate until completely cold.
08 - Heat heavy cream in small saucepan until bubbles form around edges. Place chopped dark chocolate and black cocoa powder in heatproof bowl. Pour hot cream over chocolate. Let stand 3 minutes, then whisk until completely smooth and glossy.
09 - Place one cooled cake layer on serving plate. Using small knife, carefully cut and remove shallow circular well from center, leaving 1-inch border around edges and bottom intact.
10 - Spoon chilled cherry compote into hollowed cavity, mounding slightly above surface. Position second cake layer directly on top, pressing gently to adhere.
11 - Pour room-temperature ganache over assembled cake, using offset spatula to spread evenly over top and sides. Work quickly as ganache begins setting upon contact. Refrigerate 30 minutes until firm.
12 - Use red food coloring gel to draw branching vein patterns on cake surface. Shape fondant or piped chocolate into spider forms. Position spiders decoratively and finish with edible glitter.