1Preheat oven to 350°F and grease a 9x13 baking dish.
2In a large bowl, mix pumpkin, milk, eggs, sugar, and cinnamon until well blended. Spread pumpkin mixture in prepared baking dish. Mixture will be very wet.
3Sprinkle cake mix evenly on top of the batter. If adding pecans, sprinkle them over the cake mix. Pour melted butter over the top of the cake mix. Bake 50 minutes.
4Cool completely. Top with whipped cream or ice cream.