Preheat the oven to 350 °F.
Combine the cake mix, egg and 8 tablespoons of melted butter in a medium
bowl and mix well with whisk or wooden spoon. Using your fingers, push the
mixture into the bottom of a lightly greased 9 x 13 pan.
In the bowl of a stand mixer or using an electric mixer, beat the cream cheese, eggs, pumpkin puree, vanilla, cinnamon and 8 tablespoons of melted butter until smooth. Add the powdered sugar and mix well.
Spread over the cake batter. Sprinkle the pecan streusel evenly over the top and bake for about 45 minutes. Do not over bake as the center should be a little gooey! Allow to cool slightly before slicing.