Preheat oven to 350 degrees. Spray 2 8 x 3-inch cake pans line the bottom of each pan with parchment.
Whisk flour, cocoa and salt in a bowl.
Place oil and sugar in bowl of an electric mixer fitted with the paddle attachment and beat at medium speed until well blended. Beat in eggs one at a time. With machine on low, very slowly add red food coloring and vanilla (Take care: it may splash.) Add flour mixture alternately with buttermilk in two batches. Scrape down bowl and beat just long enough to combine.
Place baking soda in a small dish, stir in vinegar and add the mixture to batter with the machine running. Beat for 10 seconds.
Divide batter among cake pans, place in oven and bake until a cake tester comes out clean, about 30 to 40 minutes. Let cool completely.
In the bowl of a stand mixer fitted with the paddle attachment, beat the butter until soft. Add the powdered sugar, cream cheese, salt and vanilla. Beat on medium high until light and fluffy about 5 minutes.
Once the cakes are cooled, cut the tops of the cakes level, reserve the scraps. Divide each cake evenly into two layers. Using a 3 or 3 ½-inch cookie cutter, punch out the center of two of the cake layers. Reserve the scraps.
Place 1 of the whole cake layers on the cake board or plate and spread a thin layer of cream cheese frosting on top. Place the second whole cake layer on top. Pipe or spread a ring of frosting on the outside of the top layer and add one of the punched layers on top. Pipe or spread a layer of frosting on top of the ring of cake and add the final punched layer. Apply a thin coat of frosting around the sides of the cake.
Line the bowl with plastic wrap letting it come up over the sides. Add a little bit of cream cheese frosting to the bottom of the bowl and spread it up the sides. Place pieces of the cake scraps into the bowl to approximate layers, adding frosting as needed. Make a 3 to 3 ½ inch hole in the center of the bowl (to match up with the hole in the center of the layer cake). Place the bowl in the freezer for 3 hours. Place the cake in the fridge. Keep the remaining frosting covered at room temperature until ready to finish assembly.
Remove the cakes from the fridge and freezer. Using the plastic wrap to help, pull the cake dome out of the bowl. Remove the plastic wrap.
Fill both holes with the candy. Spread a thin layer of frosting on the top ring of the layer cake. Flip the dome of cake on top. To prevent the candy from falling out of the top, I recommend placing a piece of cardboard over the bottom of the cake dome, flipping it upside-down, using the cardboard to prevent spillage then sliding the cardboard out once the dome is almost touching the base cake.
Use the remaining frosting to smooth out and even the entire cake. Place cake in the fridge or freezer to firm while you get the decorations ready.
Roll out the black fondant to ¼ inch think, spread the top with sanding sugar then use the rolling pin to press it inches Cut out desired eyes and mouth.
Roll the white fondant, using cornstarch to prevent sticking, to ¼ inch thick in a roughly 16-inch circle.
Remove the cake from the fridge. Roll the fondant around the rolling pin and place over the cake. Using corn starch on your hands, work the fondant down from the top, letting it drape and form ghost-like pleats.
Use water to adhere the eyes and mouth. Refrigerate until ready to serve.