Preheat the oven to 350°F and lightly grease a 9x13-inch baking dish.
In a large mixing bowl, whisk together the pumpkin purée, evaporated milk, eggs, sugar, and pumpkin spice until smooth and well combined.
Pour the pumpkin mixture evenly into the prepared baking dish.
Sprinkle the dry yellow cake mix evenly over the pumpkin layer. Do not stir.
Slowly drizzle the melted butter over the dry cake mix, trying to cover as much of the surface as possible.
Bake for 50 to 55 minutes, or until the top is golden brown and the center is set.
Let the pumpkin dump cake cool for 15 to 20 minutes before serving. Enjoy warm with whipped cream, vanilla ice cream, caramel sauce, or chopped pecans if desired.