For topping
1/4 cup all purpose flour
1/4 cup (packed) golden brown sugar
3 tablespoons unsalted butter, room temperature
1/2 teaspoon ground cinnamon
For cake
Nonstick vegetable oil spray
1 1/2 cups all purpose flour
1/4 cup (packed) golden brown sugar
2 teaspoons baking powder
1/2 teaspoon baking soda
1/2 teaspoon salt
1/2 cup unsweetened applesauce
1/3 cup low-fat buttermilk
2 tablespoons vegetable oil
1 large egg yolk
1 teaspoon vanilla extract
1/2 teaspoon (packed) grated lemon peel
2 large egg whites
Recipe
Make topping:
Preheat oven to 350°F. Combine all ingredients in small bowl. Mash with fork until blended and coarse crumbs form. Set aside.
Make cake:
Spray 9-inch-diameter cake pan with 1 1/2-inch-high sides with vegetable oil spray. Sift flour, sugar, baking powder, baking soda and salt into large bowl. Whisk applesauce, buttermilk, oil, egg yolk, vanilla and lemon peel in medium bowl until well blended. Add to dry ingredients and stir just until moistened (batter will be thick). Beat egg whites in another large bowl until stiff peaks form. Whisk half of whites into batter. Fold in remaining whites.
Transfer batter to prepared pan. Sprinkle topping over batter. Bake cake until tester inserted into center comes out clean, about 30 minutes. Transfer to rack; cool in pan. Cut into 10 wedges and serve.