Preheat oven to 200C. Lightly whisk egg whites until foamy. Set aside. Sift flour and icing sugar into a bowl, add ground almonds and lemon rind and mix well. Stir in butter and egg whites and beat with a wooden spoon until smooth. Add berries and gently fold into mixture. Grease friand tins with softened butter or cooking spray. Spoon mixture into tins and bake for 25 minutes, or until cooked when tested with a skewer. Cool in tins for five minutes before turning out on a wire rack to cool.