Dump pumpkin puree, cake mix, pumpkin spice, and butter into your crock pot in that order. Turn it on high and allow it to cook for 2 hours.
After the 2 hours are up, stir all the ingredient thoroughly to combine. Sprinkle the the brown sugar over the top. Re-cover your crock pot and cook on high for an additional 1.5 hours.
Serve by scooping the cake out with a big spoon and topping with whipped cream or vanilla ice cream.