1.Preheat oven to 180°C. Grease a 20cm baba pan well, or grease deep 20cm (8 inch) round cake pan and line base and side with baking paper.
2.Beat ingredients in medium bowl with electric mixer on low speed until combined. Increase speed to medium and beat about 3 minutes or until mixture is smooth and changed to a paler colour.
3.Spread mixture into pan; bake about 55 minutes. Stand cake in pan 5 minutes before turning onto wire rack to cool.
4.To make glacé icing, sift icing sugar into a small heatproof bowl. Stir in butter and enough of the water to make a firm paste. Stir over small saucepan of simmering water until icing is spreadable. Stir in rind.
5.Spoon icing over cold cake.