Sift together dry ingredients. Cut butter into dry ingredients. Stir in egg yolk. Pat into buttered 20 cm square pan. Bake at 180ºC or 15 minutes. While cake bakes, beat egg white until stiff, and beat in confectioner's sugar and ground almonds. When cake is set and light golden brown, remove from oven, spread with jam and then almond meringue mixture. Brown at 230ºC or 5-10 minutes.