Prepare the Crust: Preheat the oven to 350°F (175°C). Grease and flour a 9x13-inch baking pan.
Make the Crust: In a medium-sized bowl, combine the yellow cake mix, egg, and melted butter. Stir until fully combined. Press the mixture evenly into the bottom of the prepared baking pan to form the crust.
Prepare the Filling: In a separate bowl, beat the softened cream cheese until smooth using an electric mixer. Add the eggs, vanilla extract, melted butter, powdered sugar, and salt. Continue mixing until the filling is smooth and well combined.
Assemble the Cake: Pour the creamy filling over the prepared crust, spreading it evenly with a spatula.
Bake: Place the pan in the preheated oven and bake for 40-45 minutes, or until the top is golden brown and a toothpick inserted in the center comes out with just a few moist crumbs (it should not come out completely clean).
Cool and Serve: Let the cake cool completely in the pan before cutting into squares. Dust with additional powdered sugar, if desired, for an extra sweet touch.