Preheat the oven to 350°F. Spritz a 13x9-inch baking pan with cooking spray. Set aside. (You can also lightly grease with butter.)
In a large bowl use an electric mixer to beat together the cake mix, 1/2 cup melted butter and 1 large egg on medium speed until fully moistened. Press cake mixture evenly onto the bottom of the prepared pan.
In the same mixing bowl beat together the cream cheese, powdered sugar. remaining 1/2 cup of melted butter and vanilla extract.
Add 3 large eggs. Continue to beat the cream cheese mixture for 2 minutes until creamy and fluffy and no lumps remain.
Fold the crushed pineapple and flaked coconut by hand. Pour pineapple filling over the cake mix crust.
Place into the oven. Bake for 40-45 minutes or until the center still has slight movement when gently shaken and the top is golden brown. Cool in the pan on a wire rack to room temperature before cutting into bars.
Store leftovers chilled in an airtight container for up to 5 days.
Notes
Flavoring Variations - You can add coconut extract for more coconut flavor or substitute pineapple extract in place of vanilla extract to amp up the pineapple flavor.
Nuts - You could sprinkle the top with chopped pecans, macadamia nuts or almonds for texture and crunch.
Cake Mix Substitutions - You could also use a pineapple cake mix or a butter cake mix in place of yellow cake mix. Regular cake flour or all purpose flour, isn't going to work the same as a boxed mix for this recipe.
Drain the Crushed Pineapple Well - It's important to fully drain all of the pineapple juice from the crushed pineapple before adding it to the filling.
Don't Overbake - It's important not to overbake chess bars. The center should still have a slight movement when the pan is gently shaken. This is one rare moment in baking where the toothpick method doesn't work.