Bring cream cheese and eggs to room temperature. Melt butter and allow it to cool slightly.
Preheat oven to 350 degrees Fahrenheit. Lightly grease 13 x 9 baking pan.
Starting with the bottom layer, mix together cake mix, egg, pumpkin pie spice, and melted butter until it comes together. It will turn into a cookie dough-like texture.
Place the dough onto a baking pan. Use your fingers and press the dough to cover the bottom.
Beat together cream cheese until smooth. It’s important to use room temperature so you don’t get these small bits of cream cheese in the final mixture.
Add in the pumpkin purée, butter, eggs, vanilla, salt, and pumpkin pie spice (here you can play with the flavoring, substitute cinnamon, ginger, cloves, and nutmeg instead of pumpkin pie spice to your liking).
Add powdered sugar to the mixture a little bit at a time until it's all mixed together.
Pour the filling onto the cake dough and spread evenly.
Bake for about 50 or 60 minutes. This will be a judgment call. You want the center to be a little loose (and gooey) that's normal. Don’t bake past this point.
Remove from oven and cool completely. For the best texture and flavor, cover and place it in the refrigerator overnight.
To serve cut into squares. Top with whipped cream and or a single pecan.