Preheat your oven to 350°F and prepare a 9×13-inch pan by lining the bottom and sides with parchment paper.

In a mixing bowl, combine the yellow cake mix, melted butter, pumpkin pie spice, and finely chopped pecans. Mix until everything is well combined, resembling coarse crumbs.

Press about half of this mixture firmly into the bottom of the lined pan to form the crust.

In a separate bowl, stir the softened cream cheese until smooth, then add the sweetened condensed milk, egg, and vanilla, whisking until completely smooth.

In another bowl, combine pumpkin puree, eggs, sugar, evaporated milk, flour, and pumpkin pie spice. Whisk until smooth and uniform.

Alternate dollops of the cream cheese filling and the pumpkin filling over the prepared crust in the pan.

Gently swirl the two fillings together with a butter knife to achieve a marbled look, careful not to overmix.

Sprinkle the remaining crust mixture over the top of the marbled fillings.

Bake in the preheated oven for 35-40 minutes until set and no jiggle appears when you gently shake the pan.

Allow the bars to cool to room temperature in the pan, then refrigerate until ready to serve.