How to Make It
Preheat oven to 350°F. Lightly grease a 13- x 9-inch metal baking pan with cooking spray. Whisk together pumpkin, evaporated milk, eggs, sugar, and salt in a medium bowl; pour mixture into prepared pan.
Stir together cake mix, pecans, and melted butter in a medium bowl, forming a crumbly mixture. Sprinkle mixture evenly on top of pumpkin mixture in pan. Bake in preheated oven until center of cake is set and golden, 40 to 42 minutes. Cool cake completely on a wire rack before serving, about 2 hours. Chill after cooled, if desired. Cut cake into 12 squares. Serve with whipped cream.