1. In a large bowl whisk together pumpkin purée, evaporated milk, eggs, sugar, and cinnamon until smooth.
2. Pour mixture into a greased 9x13 baking dish.
3. Evenly sprinkle over dry cake mix.
4. Pour over melted butter.
5. Bake 50 minutes on 350°F. Let cool for an hour before covering and placing in the fridge.
6. Slice and serve with whipped cream!
