Grind the almonds and set aside. Place the saffron threads in a cooking spoon and heat, then crush to powder with a teaspoon. Combine powder with butter and sugar and beat until creamy. Gradually add egg while continuing to beat, then beat in lemon juice. Sift together the flour, corn starch, and baking powder. Combine the dry ingredients with the butter mixture and the almond and form into a ball. Wrap ball in plastic wrap and chill for anhour. Roll out half the dough on a floured board to about 0 cm thick, sprinkle top with granulated sugar and cut into 5 cm rounds. Place on a buttered baking sheet and bake at 180ºC or 10-12 minutes, until edges are just beginning to turn golden. Cool on racks. repeat with remaining dough.