Pumpkin Dump Cake

I got the recipe from a girl on thenest.com. I never thought I was much of a pumpkin kind of girl...but this is YUMMY!!!!

1 can pumpkin
1 lg can evaporated milk
3 eggs
1 cup sugar
4 tsp pumpkin pie spice
1 box yellow cake mix
3/4 c butter, melted
chopped walnuts (optional)

Mix together pumpkin, milk, eggs, sugar and spice in a bowl. Pour in a greased 13x9 inch pan. Pour cake mix on top and the pour melted butter on top of cake mix. Top with walnuts. Bake at 350 for 45 min-1 hr, or until a toothpick comes out clean.