Preheat the oven to 350 degrees and spray an 8x8 or 9x9 baking dish with non-stick spray.
Combine the Crust Ingredients: spice cake mix, 1 egg and ½ cup of melted butter. Spread in the baking dish (see photo).
Combine the Filling Ingredients: canned pumpkin, 2 large eggs, ½ cup of sugar, ¼ cup of packed brown sugar and cinnamon. Pour over the crust (see photo).
Combine the crumble topping ingredients: 1 cup of reserved spice cake mix, ½ cup of sugar, ¼ cup of melted butter and cinnamon (see photo) and spread evenly over the top of the filling mixture (see photo).
Bake 40-45 minutes. Insert a toothpick around 35-40 minutes. If it comes out clean the crumble is done.
Allow to cool completely prior to cutting and serving. Best stored in the fridge as it will get soft if left out.