Preheat oven to 350 degrees F. Prepare a 9" X 13" baking pan by lining it with criss crossed pieces of aluminum foil that have an overhang of an inch or two. Spray with cooking spray unless using non-stick aluminum foil.
Cream the powdered sugar and butter in a stand mixer until light and fluffy. Add 2 cups of the flour and beat on medium speed until mixed. Press into the bottom of the prepared baking pan and bake for 15-20 minutes or until golden.
Beat the eggs, sugar, Meyer lemon juice and lemon zest in a large bowl either by hand or with a mixer. Sift the reserved 1/2 cup flour and baking powder into the mixture and mix well.
Pour over the hot crust and return to the oven to bake for another 20-25 minutes. Check for doneness at 20 minutes, and add on time as needed.
Cool completely before cutting, then dust with powdered sugar and serve.