Preheat oven to 350 degrees. Lightly grease a 9x9 cake pan.
In a mixing bowl, combine the cake mix, 8 tablespoons of melted butter and one egg. Using an electric mixer, mix on medium, until completely combined. Pat into the bottom of the prepared cake pan.
With an electric mixer, beat the softened cream cheese until smooth. Add in the remaining 8 tablespoons of melted butter, vanilla, and remaining egg. Mix until combined.
Mix in crushed pineapple. Slowly add in the powdered sugar and mix, on medium, until completely combined. Spread over the first layer of cake in the prepared cake pan.
Bake for approximately 50-60 minutes being careful not to over bake. As the name suggests says, it should be "gooey." Let cool completely before slicing into squares and serving.
Notes
To cut neat slices, cut the cooled cake using a plastic knife.
Store cooled cake pieces in an airtight container. The cake will last 2-3 days at room temperature or up to a week in the refrigerator.
To freeze: wrap tightly in plastic wrap and place in airtight storage container. Freezer for up to 3 months. To serve, simply thaw completely.