Preheat the oven to 350 degrees F (175 degrees C). Line a 9x13 inch baking pan with parchment paper or aluminum foil.
In a large bowl, stir together the pumpkin, sugar and eggs. Mix in the evaporated milk and pumpkin pie spice; pour into the prepared pan.
Sprinkle the dry cake mix over the pumpkin and then drizzle melted butter over the cake mix.
Bake for 1 hour in the preheated oven, or until a knife inserted into the cake comes out clean. Cool, then invert onto a serving dish. Serve with whipped topping.
