01 -
Heat the oven according to the cake mix box. Grease two 8-inch round cake pans and line the bottoms with parchment if you have it.
02 -
Prepare the cake batter with the eggs, oil, and water listed on the box. Stir in orange gel food coloring until the batter is evenly tinted.
03 -
Divide the batter between the pans and bake according to the box directions, usually 24-30 minutes, until a toothpick inserted in the center comes out clean.
04 -
Cool the cakes in the pans for 10 minutes, then turn them onto a rack. Let them cool completely before frosting.
05 -
Stir black gel food coloring into the chocolate frosting until very dark. Transfer to a piping bag fitted with a small round tip.
06 -
Spread vanilla buttercream between the layers. Cover the cake with a thin crumb coat, chill for 15 minutes, then add a smooth final coat.
07 -
Pipe black circles on top of the cake and drag a toothpick outward from the center to form a web. Add a few web lines down the sides if desired.
08 -
Press Mini Oreos onto the cake. Pipe 8 legs around each cookie, attach candy eyes with small dots of frosting, and add sprinkles if using.