BOTTOM LAYER: Combine flour and icing sugar in medium bowl. Cut in margarine until mixture resembles fine crumbs. Press firmly in ungreased 9 x 13 inch pan. Bake in 350°F oven for about 20 minutes until golden. Remove from oven.
TOP LAYER: Beat eggs in large bowl until frothy. Add lemon juice and peel. Stir.
Combine granulated sugar, flour and baking powder in small bowl. Add to egg mixture. Stir until just moistened. Spread evenly over bottom layer. Bake for about 25 minutes until set. Let stand in pan on wire rack for 5 minutes.
Dust evenly with icing sugar using sieve. Let stand until cool. Cuts into 48 bars.