Preheat the oven to 180.C/350'F/Gas 4. Grease a
3-litre/
5-pint/12 1/2-cup
bundt
or fluted tube tin and dust with flour.
Cream the butter and caster sugar until
light and fluffy. Add the egg yolks, one at a time,
beating well after each addition. Add the lemon
rind, juice and yogurt and stir .
Sift together the flour, baking powder and
bicarbonate
of soda. In another
bowl, beat the egg whites and salt until they
hold stiff peaks.
Fold the dry ingredients into the butter mixture,
then fold
in a dollop of egg
whites.
Fold in the remaining whites.
Pour into the
tin and bake until a skewer inserted in the
centre comes out clean, about 50 minutes. Leave
in the tin for 15 minutes, then turn out and
cool on a wire rack.
For the glaze,
sift the icing sugar into a bowl. Stir in the lemon
juice and just enough yogurt to make a smooth glaze.
Set the
cooled cake on the wire rack over a sheet of
greaseproof paper. Pour over the glaze and allow
to set.