Preheat oven: Preheat your oven to 350°F (175°C). Lightly grease a 9x13-inch baking dish or leave ungreased.
Mix pumpkin layer: In the baking dish, combine pumpkin puree, evaporated milk, sugar, and pumpkin pie spice. Whisk until smooth and well combined.
Add cake mix: Evenly sprinkle the dry cake mix over the pumpkin mixture, covering the entire surface. Use a spoon to distribute it if needed.
Drizzle butter: Pour the melted butter evenly over the cake mix, making sure to cover all areas, especially the edges.
Bake: Bake for 50-60 minutes, until the top is golden brown and set. The edges should be bubbly and the cake layer should have a crispy crust.
Cool and serve: Let cool for 15 minutes before serving. Serve warm with vanilla ice cream or whipped cream.
