Preheat the oven to 350ºF. Spray a 9x13-inch baking dish with nonstick cooking spray.
In a bowl, combine the pumpkin puree, evaporated milk, sugar, eggs, pumpkin pie spice, and cinnamon.
Pour the mixture into the bottom of the prepared pan.
Sprinkle the cake mix evenly over the top, then sprinkle the pecans over.
Melt 1/2 cup of the butter and pour evenly over the top of the cake mix.
Take the remaining 1/2 cup of butter and thinly slice it. Place the butter slices evenly over the top of the cake.
Bake the cake in the preheated oven until the top is golden brown and the edges are bubbling, about 45-50 minutes.
Let the cake sit for 10 minutes before slicing.
Serve warm with ice cream or whipped cream, if desired.
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Notes
*Cake mixes can range from 15.25 oz to 13.25 oz - anything in this size range will work.Nutrition information provided as an estimate only. Various brands and products can change the counts. Any nutritional information should be used as a general guide.