Step 1. Preheat oven to 350 degrees. Prep a 9 inch springform pan wot sith nonstick baking spray.
Step 2. Cut a sheet of parchment paper to fit the bottom of the springform pan. Lay the cut parchment paper in the bottom of the pan.
Step 3. Whisk the flour, sugar, and cinnamon in a bowl for the streusel. Set aside. Add flour, pumpkin pie spice, baking soda, salt, and baking powder to a bowl. Whisk to combine for the cake, Set aside.
Cake:
Step 1. Add the butter and sugar together in a large mixing bowl. With an electric mixer, cream the butter and sugar.
Step 2. Add one egg at a time, beating immediately after each addition until combined. Stir in milk,vanilla, pumpkin, and sour cream until well mixed.
Step 3. Alternate adding some of the flour mixture and the milk mixture in with the buttered sugar mixture.
Step 4. Use the electric mixer to blend all of the ingredients together. Pour the cake batter into the springform pan.
Streusel:
Step 1. Add the melted butter to the prepared streusel mixture. Use a fork to mix until the streusel is crumbly.
Step 2. Pour the streusel topping on the cake.
Step 3. Bake at 350 degrees for 40-50 minutes. (Test to make sure the cake is done by inserting a toothpick in the center of the cake. If the toothpick comes out clean, the cake is done.)
Step 4. Serve warm.