Cake:
1 1/3 cups granulated sugar
6 tablespoons butter, softened
1 tablespoon grated lemon rind
3 tablespoons thawed lemonade concentrate
2 teaspoons vanilla extract
2 large eggs
2 large egg whites
2 cups all-purpose flour
1 teaspoon baking powder
1/2 teaspoon salt
1/2 teaspoon baking soda
1 1/4 cups fat-free buttermilk
Cooking spray
Frosting:
2 tablespoons butter, softened
2 teaspoons grated lemon rind
2 teaspoons thawed lemonade concentrate
1/2 teaspoon vanilla extract
8 ounces 1/3-less-fat cream cheese
3 1/2 cups powdered sugar