Combine all dry ingredients (flour, sugar, baking soda & powder, salt, and spices) in a stand mixer with a paddle attachment on speed 1.
Add all remaining ingredients and mix until combines, scraping the bowl to ensure a homogeneous mixture.
Divide the batter evenly between two 9 inch pans lined with pan spray and parchment. Bake 28-35 minutes at 350F. The cakes are done when a toothpick comes out cleanly when poked in the center of the cake. Allow time to fully cool on a cooling rack.
Cald the cream in a small saucepan or microwave. Pour over combined chocolate and corn syrup, stir with a whisk until smooth and homogeneous. Stir in rum and cinnamon, allow the mixture to set in a shallow pan or plate at room temperature before using (at least 30 minutes). If the mixture sets to a point where it's no longer spreadable, simply microwave it and stir it for very small intervals (5 seconds at time in the microwave).
Assemble the cake:
Cut each round into two thin layers, if desired. Divide the rum ganache in three portions and spread evenly to the tops of three of the four layers of cake. Plop about 3/4 cup of the hazelnut frosting on top of each spread ganache layer, and spread evenly as well. Stack all four layers of the cake, the one that has no ganache or hazelnut frosting will be the top layer. Spread the remaining hazelnut frosting over the top and sides of the cake. If desired, you can do a very thin layer of frosting, then refrigerate, then add remaining frosting to avoid crumbs in your top layer. !To make the marzipan pumpkins:
Add the food coloring to the marzipan and mix well with hands like it was play dough until all of the color is even. Divide the dough into 9 equal sized portions. Use hands to roll each portion into a ball and then use butter knife to indent grooves down the side to make it look like a pumpkin. Insert a whole clove into the top for the stem. Top cake with marzipan pumpkins.