Preheat the oven to 350°F (175°C) and lightly grease a 9×13-inch baking pan. In a medium bowl, mix together the yellow cake mix, melted butter, and one egg until a thick, smooth dough forms.
Press it evenly into the bottom of the pan, dusting your fingers with powdered sugar if the dough feels sticky.
In a large bowl, beat the softened cream cheese until smooth. Add the pumpkin puree, eggs, melted butter, and vanilla, mixing until creamy and well-blended.
Stir in the spices, then gradually beat in the powdered sugar until smooth, fluffy, and rich.
Pour the pumpkin mixture over the cake base, spreading it evenly to the edges. Bake for 45–50 minutes until the edges are set but the center still has a slight jiggle for that gooey texture. Let the cake cool completely before slicing.
Dust the top with powdered sugar, slice into squares, and serve with whipped cream, caramel drizzle, or toasted pecans.