I've made this a few times and kept meaning to post the recipe because it's so tasty. This last time I remembered to snap a photo just before the last morsel disappeared.
2 cups all-purpose flour, 1 teaspoon baking powder, half teaspoon salt, quarter teaspoon baking soda, 3/4 cup sugar, half cup applesauce, 1 cup fat-free yogurt, 6 tablespoons egg whites
Quarter cup sugar2 teaspoons cinnamon2 teaspoons vanillaquarter cup chopped walnuts
Mix the wet and dry ingredients separately, then mix them together, pour into a 9" x 12" dish. Spread the topping and bake at 350 degrees for 35 minutes.