Add the filling ingredients to a large mixing bowl and whisk well to combine.
Spray a 9 inch standard plate with non-stick spray. Pour filling into pie plate.
Bake for 45 minutes. Filling will still be somewhat jiggly.
Add the topping ingredients to a small mixing bowl and stir to combine.
Sprinkle the streusel evenly over the pie and return to the oven for 15-20 minutes or until a knife inserted in the center comes out clean.
Cool on the counter for 1 hour before transferring to the refrigerator to cool completely, about 3 hours.
Notes
If you don't have pumpkin pie spice, you may use 2 teaspoons cinnamon, 1/2 teaspoon nutmeg, 1/2 teaspoon ginger, and 1/4 teaspoon cloves in it's place.