Preheat your oven to 350°F. Grease a 9×13-inch baking pan with nonstick spray and set aside.
In a mixing bowl, combine the yellow cake mix, egg, and unsalted butter. Mix well using a hand mixer until fully combined. Pat the mixture into the bottom of the prepared baking pan. Set aside as you prepare the filling.
In a large bowl, beat the cream cheese and pumpkin puree together until smooth. It’s important to ensure there are no lumps. This will create a perfectly creamy filling.
Add in the eggs, pure vanilla extract, and melted unsalted butter to the cream cheese mixture. Beat until everything is combined and smooth.
Next, add the powdered sugar, ground cinnamon, and ground nutmeg. Mix well until the filling is well combined. The spices will bring out the pumpkin flavor beautifully.
Spread the pumpkin mixture evenly over the cake batter in the baking pan. Ensure an even layer for consistent baking.
Bake in the preheated oven for 40 to 50 minutes. Keep an eye on it; the center should be slightly gooey, but the edges should be set. Don’t overbake!
Once baked, let the cake cool slightly. You can serve it warm, or let it cool completely. Top with whipped cream, chopped pecans, or caramel sauce for extra indulgence.