This moist and autumnal scented cake is a great way to use leftover pumpkin puree that you might have leftover. The pumpkin makes the cake moist with a lovely toothsome bite, while the pecan crumb topping and pumpkin spice filling makes this a classic. Serve it with tea or coffee in the afternoon or for breakfast on a cold winter day.
Preheat the oven to 350°F. Place a 9-inch springform pan on a piece of aluminum foil and wrap the bottom of the pan tightly with the foil to keep any cake batter from leaking. Lightly spray the bottom and sides of the pan with cooking oil, then line the bottom with parchment paper. Place on a baking sheet and set aside.
Make the streusel filling by combining flour, white sugar, chopped pecans, dark sugar, pumpkin spice blend and salt in a medium size bowl. Stir together until mixed, then drizzle the melted butter over the dry ingredients, tossing with a fork until the butter has been absorbed and the ingredients have clumped up. Refrigerate uncovered while you prepare the remaining cake.
Make the filling by combining the dark brown sugar, pumpkin spice and cocoa powder (if using) in a small bowl and mixing with a fork until uniform in color.
Make the cake batter by placing the sugar, vegetable oil, vanilla extract, pumpkin spice, and salt in a large bowl. Mix with a whisk until well blended.
Add the eggs, one at a time, until incorporated, making sure the first one is mixed in before adding the second one. Add the pumpkin and mix in.
Add the baking powder and mix to absorb. Add the flour and gently stir it in with a large spatula or wooden spoon until all the flour is absorbed.
Carefully spoon and spread about half the batter into the bottom of the pan. Sprinkle the filling over the top of the batter, leaving about a 1/2-inch margin around the edge of the cake. Carefully spoon and spread the remaining batter over the filling.
Take the cold streusel topping out of the fridge and sprinkle it all over the top of the cake, breaking up any big chunks into small pebble sized pieces. Make sure to cover the entire cake.
Gently tap the cake on a table or counter to release any air bubbles, then bake in the oven 60 to 65 minutes or until a toothpick inserted in the middle of the cake comes out clean. If you have an instant read thermometer, the center of the cake should read 210° F.Let cool on a wire rack for at least 30 minutes before releasing the sides of the spring form pan and removing the cake to a serving platter.