Preheat oven 180C,grease large rectangular tin and line with baking paper.
Put all ingredients into a large mixing bowl and beat on a low speed until combined.
Increase speed to high and beat 2-3 minutes until pale.
Pour into baking tin and bake for 50 minutes or until golden and a skewer comes out clean when inserted into middle of the cake.
Let cool in pan for 10 minutes then turn onto wire rack to cool.
Cut into small squares.
To make a glace icing(optional)combine 1 1/2 cups icing sugar,2 tablespoons lemon juice and 1 teaspoon softened butter in a small bowl,stir with wood spoon until a spreadable consistency and spread over cake.