Preheat oven to 350 degrees. Prepare a baking dish (9X13) with non-stick cooking spray and set aside.
Whisk together pumpkin puree, evaporated milk, eggs, cinnamon, and sugar. Pour the liquid mixture into the bottom of the baking dish.
Sprinkle spice cake mix on top of pumpkin mix then drizzle on melted butter.
Bake for 60-65 minutes. Cool for 25-30 minutes. Optional: serve with whipped cream and a pinch of cinnamon.
Notes
Can I use another cake mix? You could use another cake mix for this recipe but the spice in pumpkin spice would be missing. I would suggest adding some pumpkin pie spice to your cake mix if you use another flavor.