1. Beat butter and sugar in a mixer until fluffy. Add in lemon rind and lemon juice, mix well.
2. Sift flour, baking powder and soda, fold into butter mixture together with crushed biscuit, mix until forms dough.
3. Wrap well the dough and refrigerate for I hour.
4. Roll out the dough between two sheets of plastic paper, about 5mm. Cut out watermelon shapes and place on to the baking tray.
5. Bake in preheated oven at 160C for 15-20 minutes or until golden brown.
6. When cool, decorate with ornamental icing. When the icing was solidification, keep into airtight container.