Cream butter & 1/2 of the powdered sugar together. Add 2 cups of flour and stir until has a dough consistency. Pat into a 9x13 baking pan. Bake at 350 degrees for 20 minutes.
Combine eggs, regular sugar, remaining powdered sugar, remaining flour, lemon juice & baking powder and put into blender or food processor. Blend together for 5 seconds; scrape off edges and blend for another 5 seconds. Pour lemon mixture over the baked crust.
Bake at 350 degrees for 25 minutes or until light brown on top; cool and sprinkle (I use my sifter) the top with powdered sugar.