CRUST: Combine sugar, flour and ground almonds in a mixing bowl. Cut in butter until mixture is crumbly. Press into a 9 X 13 inch cake pan. Bake at 350 degrees F for 15 minutes until light golden. Cool 10 minutes.
FILLING: Beat eggs, sugar and lemon juice together well.
Combine flour and baking powder; stir into eggs thoroughly. Pour over baked crust.
Bake at 350 degrees F. for 18 - 23 minutes, or just until set and light golden. Cool, then cut into bars. Sprinkle with icing sugar before serving, if desired.