Preheat oven to 350° F. Spray 8- x 5-inch loaf pan with non-stick cooking spray; set aside. Into small bowl, sift together cake flour, baking powder and baking soda; set aside.

In large bowl with electric mixer at medium speed, beat margarine, 1/4 cup sugar, 6 packets Sweet One, egg, 2 tablespoons lemon juice and lemon peel until well blended. Add flour mixture alternately with buttermilk, beginning and ending with flour and beating until smooth. In large metal bowl with electric mixer at high speed, beat egg whites and cream of tartar until stiff peaks form; fold into batter. Pour batter into prepared loaf pan. Bake 35 to 40 minutes or until wooden pick inserted in center comes out clean. Cool on wire rack 10 minutes. Remove from pan; cool completely on wire rack.

Meanwhile, prepare glaze: In small saucepan over medium heat, combine 1 tablespoon sugar, 2 packets Sweet One, water and 2 teaspoons. lemon juice; bring to a boil. Cook 2 to 3 minutes or until mixture is thick and syrupy. Brush on top of cooled tea loaf.