Great Pumpkin Dessert

I don't remember where I got this one, but it's been a hit when I've made it.

Ingredients:
1 Can (15 oz) Solid Pack Pumpkin
1 Can (12 oz) Evaporated Milk
3 eggs
4 Teaspoon Pumpkin Pie Spice
1 Cup Sugar

1 Package yellow Cake Mix
3/4 Cup Butter, melted
1 1/2 Cups Chopped Walnuts

Directions:
In Mixing Bowl, Combine Pumpkin, Evaporated Milk, Eggs, Pie Spice, and Sugar. Pour into greased 13x9x2 inch baking pan. Sprinkle dry cake mix on top then drizzle with melted butter. Top with Walnuts and bake for 1 hour in a 350 degree oven. Serve with Vanilla Ice Cream or whipped cream.