How to Make It
Make Crumble: Preheat oven to 300°F. In a bowl, stir together all Crumble ingredients except the pumpkin seeds with a mixing spoon until a crumbly dough forms, about 2 minutes. Scatter dough across a parchment paper-lined baking sheet. Bake for 10 minutes, stirring the crumble halfway through baking. Add pumpkin seeds, stir to combine, and return to oven for an additional 10 minutes, stirring again halfway through baking. Set aside to cool.
Make Cake: Increase oven temperature to 350°F. Grease a 10-inch springform pan with cooking spray and line the bottom with parchment paper. Set aside. In a bowl, whisk together flour, salt, baking powder, baking soda, and spices. Set aside. In a separate large mixing bowl, whisk together eggs, pumpkin, sugar, and oil until eggs are fully combined into liquid mixture. Whisk in half of the dry ingredients until well combined. Add remaining dry and whisk until no pockets of dry ingredients remain. Pour batter into prepared pan, spread evenly inside pan, and bake until a toothpick inserted in the center comes out clean, about 1 hour and 15 minutes. Allow to cool to room temperature before removing cake from pan, about 1 hour.
Make Frosting: Beat butter and cream cheese on medium-high until fully incorporated, about 3 minutes. Add vanilla, salt, and canned pumpkin; mix on medium-high until well combined, about 2 minutes. Add powdered sugar and mix on low to incorporate. Scrape down sides of bowl and increase speed to medium-high, beating Frosting for an additional 3 minutes until lightened and airy.
Assemble Cake: Use a serrated knife to remove the dome of the cake and make a level surface. Spread Frosting on top of Cake. Sprinkle Crumble evenly across Frosting.