Step 1

Preheat oven to 180°C/160°C fan forced. Line 2 x baking trays with baking paper.

Step 2

Cream butter and sugar in the bowl of an electric mixer fitted with a paddle attachment until creamy. Beat in egg, juice and rind and food colouring if using. At the lowest setting beat in flour until combined.

Step 3

Take heaped teaspoons of mixture and roll into balls, then roll in icing sugar and place on trays 3cm apart, repeat with remaining mixture.

Step 4

Bake trays of biscuits for 15-18 minutes or until crisp but not coloured. Dust with more icing sugar straight out of the oven. Allow to cool on the tray for 5 minutes before transferring to a wire rack to cool completely.