Preheat oven to 350 degrees. Grease a 9 or 9 1/2 inch deep dish pie plate generously with some butter.
Whisk together pumpkin, evaporated milk, 1 1/2 eggs, sugars, pumpkin pie spice in a medium bowl. Pour into greased pie plate.
Mix together the cake mix and softened butter to make a very soft and crumbly dough. Sprinkle over top of the pumpkin mixture, then sprinkle pecans on top.
Bake for 50 minutes or until golden brown.
Let cool to room temperature and then chill until ready to serve. To serve, bring back to room temperature.
Slice and serve with whipped cream or ice cream.