Preheat oven to 350 degrees F. Grease a 15 x 10 x 1 inch jelly-roll pan. In large mixing bowl, on low speed, combine cake mix, 1 egg, butter and 2 tsp. pumpkin pie spice until crumbly. Press mixture in bottom of prepared baking pan.
In large mixing bowl, beat cream cheese until fluffy. Gradually beat in sweetened condensed milk, then remaining 2 eggs, pumpkin puree, remaining 2 tsp. pumpkin pie spice and salt; mix well. Pour over crust; sprinkle with nuts.
Bake 30 to 35 minutes or until set. Cool in pan on wire rack. Chill. Cut into bars. Store covered in refrigerator. Serve with whipped topping if desired.