Preheat your oven to 350°F (175°C) and spray a 9×13-inch baking dish with nonstick cooking spray.

In a mixing bowl, combine the pumpkin puree, evaporated milk, eggs, sugar, and cinnamon. Whisk until smooth.

Pour the pumpkin mixture into the prepared baking dish, spreading it evenly.

Sprinkle the spice cake mix evenly over the pumpkin mixture without stirring.

Drizzle the melted butter over the spice cake layer evenly.

Bake for about 55-60 minutes until edges are golden brown and the center has a slight jiggle.

Let it cool for at least 30 minutes before serving.