In a large bowl, combine the dry cake mix, the 1/2 cup butter, and 1 of the eggs, beating until combined. Reserve 1 cup of mixture.
Spread remaining mixture in an ungreased 13x9x2-inch baking pan, pressing to form an even crust.
For filling, in a medium bowl, beat together the remaining eggs, the pumpkin, evaporated milk, brown sugar, and pumpkin pie spice. Pour the mixture over the prepared crust.
Combine the reserved 1 cup cake-mix mixture, granulated sugar, the 2 tablespoons butter, and the cinnamon. Dot evenly over pumpkin filling.
Bake in a 350 degree F oven for 45 to 50 minutes or until knife inserted near center comes out clean. Cool in pan on wire rack. Cut into squares. Serve topped with whipped cream. Store in the refrigerator. Makes 12 servings.