Preheat oven to 350F degrees. Coat a 9x13 baking pan with nonstick cooking spray.
In a large mixing bowl, combine the pumpkin, evaporated milk, eggs, sugar, vanilla, cinnamon and pumpkin pie spice. Pour the mixture into the prepared baking pan.
Sprinkle the cake mix in an even layer over the pumpkin layer.
Slice the cold butter into thin slices and arrange them evenly over the cake layer. Then, sprinkle the chopped pecans over top.
Bake for 1 hour and 15 minutes. Allow to cool completely before serving.