2 1/4 c. cake flour, sifted
2 tsp. baking powder
1/2 tsp. salt
1 3/4 c. sugar
8 oz. non-fat plain yogurt
3 tbsp. oil
1 tbsp. fresh lemon juice
1 tsp. grated lemon peel
1/2 tsp. vanilla
4 lg. egg whites, stiffly beaten

STREUSEL:

1/4 c. brown sugar, packed
1/4 c. uncooked oats

Mix cake flour, baking powder and salt. Beat sugar, plain yogurt, oil, lemon juice, grated lemon peel and vanilla. Add dry ingredients. Fold in 4 large stiffly beaten egg whites. Pour into cupcake papers. Top with streusel. Bake at 350 degrees for 35 to 40 minutes.