Preheat oven to 350 degrees. Spray a 9x13 baking dish with cooking spray and set off to the side.
In a large bowl mix together pumpkin puree and evaporated milk.
Add the 3 beaten eggs and mix slightly.
Add the pumpkin pie spice, sugar, and pinch of salt and mix well.
Pour the pumpkin mixture into prepared baking dish.
Slowly pour the dry cake mix over the pumpkin mixture evenly. Don't push into the mixture.
Drizzle the melted butter over the dry cake mix evenly.
Optional: Sprinkle chopped pecans on top.
Bake for 50-60 minutes. The top layer should be completely cooked making the pumpkin mixture on bottom cooked also.
Allow to cool to room temperature. Top with cool whip. Enjoy.