Preheat the oven to 150C/300F/Gas mark 2
Grease an 8 inch round sandwich tin. Cream the butter and sugar together until very soft, pale and fluffy. Add the orange juice and rind. Work in the flour and make a soft dough. Lightly knead the dough together in a bowl, then press into the prepared tin. Prick the shortbread all over with a fork. Chill the shortbread for 30 minutes.
Bake the shortbread for 40-45 minutes, until firm and lightly browned on top. Cut into wedges at once but do not remove from the tin. Sprinkle with caster sugar while hot. Leave the shortbread in the tin until it is firm enough to lift out.
