Preheat the oven
to 190'C/375'F/Gas 5. Generously grease a 12 -cup
Madeleine cake tin. Sift together the flour and the
baking powder.
Beat the eggs and
icing sugar until the mixture is thick and creamy
and leaves ribbon trails. Gently fold in the lemon
or orange rind and juice.
Beginning with
the flour mixture, alternately fold in the flour and
melted butter in four batches. Leave to stand for 10
minutes, then spoon into the tin. Tap gently to
release any air bubbles. Bake for 12-15 minutes,
rotating the tin halfway through cooking, until a
skewer inserted in the centre comes out clean. Tip
out on to a wire rack to cool completely and dust
with icing sugar before serving.