In a small bowl whisk together the flour, baking powder and salt, set aside.
In a medium sized bowl or a large measuring cup beat the room temperature eggs and sugar with a hand mixer until pale, thick, and the volume has almost doubled.
Gently beat in the juice and rind, then add the flour mixture until just incorporated.
Pour over the base and bake for 20 to 25 minutes or until golden brown and set in the middle.
Allow to cool completely.
Once cooled sprinkle with icing sugar.
Cut into squares, or if you want smaller pieces into triangles.