1.Preheat oven to 160°C. Grease deep 23cm square cake pan; line base with baking paper.
2.Stir golden syrup, water, sugar and butter in large saucepan over low heat until smooth. Bring to the boil. Remove from heat; cool to room temperature. Stir in sifted dry ingredients, in two batches. Pour mixture into pan.
3.Bake cake for about 1¼ hours. Stand cake in pan for 5 minutes before turning, top-side up, onto wire rack to cool.
4.LEMON ICING: Beat butter and rind in small bowl until smooth; gradually stir in juice and sifted icing sugar.
5.Spread cold cake with lemon icing. Cut into 16 squares.
Store in an airtight container for up to a week.Note