Apple Annie's Lemon Squares

When I need a quick dessert and know that I have everything that I need, this is a good choice.  It makes a huge ammount so it is good to make when you are taking a meal to someone.This is a recipe from the Express News of San Antonio they got from a cafe in my neighborhood.
Printable Version:
https://sites.google.com/site/whatscookingsherry/apple-annie-s-lemon-squares
Ingredients for the base:
2 cups flour
1 cup (2 sticks) butter, cut into bits
1/2 cup powdered sugar
Ingredients for the Filling:
4 eggs 2 cups sugar
4-6 tablespoons fresh lemon juice
1 tablespoon lemon rind (just the zest, with none of the white pith)
1/4 cup flour
1 teaspoon baking powder
Powdered sugar, for garnish
Directions:
For the base: Preheat oven to 350 degrees. Cream together flour, butter, and powdered sugar. Press evenly into an ungreased 11" X 15" jellyroll pan. Bake 20 minutes, just until edges are golden.
 For the Filling:  In a mixing bowl, beat together eggs, sugar, lemon juice, lemon zest, flour and baking powder. Pour over baked crust. Return to oven and bake 20-25 minutes. Remove from oven and let cool. Sift with powdered sugar and cut into 2 inch squares.