Pumpkin Patch Dessert

2 - cans pumpkin (15-ounce)
1 teaspoon salt
4 eggs
12-ounce evaporated milk
1½ cups sugar
3 teaspoons pumpkin pie spice
1 box yellow cake mix
1 cup melted butter 
1/2 cup chopped nuts, optional
  
   Mix together pumpkin, salt and eggs. 
 Beat well and add evaporated milk. 
Stir in sugar and spice.  
Pour into a 9 x 13 pan (no need to grease). 
Sprinkle cake mix over the top.  
Pour melted butter over the cake mix. 
Sprinkle on nuts.  Bake at 350 for 1 hour. 
Top each serving with whipped cream.