Preheat the oven to 180oC/350oF/Gas
4. Grease a 3 liter 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 center 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.