• Grease and flour a baking tray. Put the flour and salt in a mixing bowl. Rub in the butter, then stir in the sugar and lemon rind.
• Lightly work the mixture together until it forms a smooth stiff ball of dough. Roll into a 20 cm (8 in) circle and place on the baking tray.
• Pinch the edges, prick the middle all over with a fork and cut the shortbread into eight wedges. Chill for 15 minutes.
• Bake in a moderate oven for 40 minutes or until pale golden. Leave on the baking tray for a few minutes, then cool completely on a wire rack.

cook's tip

• Prick biscuits evenly and decoratively with a fork before cooking to prevent them bubbling up or rising when baked. Chilling first makes a crisp, short biscuit.