Preheat oven to 350°F.
Spray a 9x13 baking dish.
Using a stand mixer or large mixing bowl, combine pumpkin puree, half and half, sugars, and pumpkin pie spice.
Add eggs one at a time, mixing well after each egg, until all ingredients are well blended.
Pour pumpkin mixture into greased 9x13 baking dish.
Spread dry yellow cake mix over the pumpkin mixture.
Sprinkle pecans over dry cake mix.
Drizzle melted butter over pecans.
In a preheated oven, bake pumpkin crunch cake for 45 to 50 minutes or until the knife inserted in the center of the cake comes out clean.
Remove cake and allow to cool completely before serving.
Serve with whipped topping, if desired.