Preheat oven to 350°F and grease a 9x13 baking dish with nonstick cooking spray.

In a large mixing bowl, whisk together pumpkin puree, evaporated milk, granulated sugar, brown sugar, pumpkin pie spice, and eggs until smooth. Pour it evenly into the prepared pan.

In a separate bowl, combine the dry cake mix with the melted butter. Stir until the mixture forms a thick batter.

Drop spoonfuls of this buttery mixture evenly across the top of the pumpkin layer. You don’t need to spread it perfectly — leaving some gaps allows the pumpkin to bubble through and creates that gooey, marbled look after baking.

Bake for about 50 minutes, or until the center is set and a toothpick inserted into the middle comes out mostly clean. The top should be golden brown and slightly crisp. If your oven runs hot, check around 45 minutes to avoid overbaking.

Let the cake cool completely before slicing. As it cools, the pumpkin layer will firm up and the buttery topping will soften slightly, giving it that signature “ooey gooey” texture.

Serve plain, or add a dollop of whipped cream or a drizzle of caramel sauce before serving. This dessert tastes great at room temperature or chilled.

Store leftovers covered in the refrigerator for up to 4 days. Reheat individual slices in the microwave for about 15 seconds for that fresh-from-the-oven taste.