Preheat oven to 350 degrees. In a bowl, mix butter, two cups flour and powdered sugar using a piecrust blender, a U-shaped hand utensil. Press dough into a greased 9" x 13" cake pan. Bake at 350 degrees for 20 minutes.
In a bowl, beat four eggs until light. Blend two cups sugar, four tablespoons flour, salt, and lemon juice. Pour topping mixture on baked crust and bake 25 minutes at 350 degrees. Cool. Sprinkle with powdered sugar and cut into bars.