Cream the butter and sugar together until it is pale and creamy. Beat the eggs well. Add the sifted flour, bicarbonate of soda, lemon rind and the beaten eggs in small amounts to the butter and sugar and ensure that they are well combined each time. Turn the dough onto a floured surface and after shaking a little flour on top, roll out to about a half to a quarter inch thick. Cut into biscuit/cookie sized rounds with a scalloped pastry cutter (if you have one) . Place in a well greased/oiled baking tray and cook in a pre-heated oven at 200C/400F/Gas Mark 6 for 20/25 minutes until light golden colour. Adjust the cooking time if you have a fan-assisted electric oven. Cool on a wire rack and dust with icing sugar/frosting when cool. Store in an airtight container.