Heat the oven to 350º F.
Grease a baking dish measuring 9 x 13 inches with cooking spray.
In a medium bowl, whisk together the pumpkin purée, evaporated milk, brown sugar, eggs, vanilla extract, spices and salt.
Pour the mixture into the prepared baking dish.
Sprinkle the dry cake mix evenly over the pumpkin mixture.
Sprinkle the toffee bits and pecans evenly over the cake mix.
Drizzle the melted butter evenly over toffee and pecans.
Bake for 45 to 50 minutes. The cake will still look a little jiggly in the middle, but it will set up.
Cool 20 to 30 minutes to let it set up, and then enjoy warm. Alternately, you can cool completely and serve at room temperature. Enjoy!