Preheat oven to 350 degrees. In medium bowl, combine 1 ½ C. flour and the confectioners’ sugar; cut in margarine until crumbly. Press into bottom of lightly greased 13 x 9 inch baking pan; bake 15 minutes. Meanwhile, in large bowl, combine eggs, granulated sugar, baking powder, lemon juice and remaining 3 Tbs. flour; mix well. Pour over baked crust; bake 20 to 25 minutes or until golden brown. Cool. Cut into bars. Sprinkle with additional confectioners’ sugar. Store covered in refrigerator, serve at room temperature.