Preheat the oven to 350 degrees. Grease an 8-inch square pan. Mix together the powdered sugar, 1/8 tsp. salt, flour and butter until a soft dough forms. Pat the dough into the greased pan and bake for 15 minutes or until lightly browned. Meanwhile, mix together the lemon juice, sugar, baking powder, salt and eggs. Remove the pan from the oven and spread the lemon mixture over the dough. Return the pan to the oven and bake for an additional 20 minutes or until golden brown. Sprinkle with powdered sugar.