Sunny Sponge Cake

Ingredients

• 3 egg yolks
• 1 cup sugar, divided
• 2 teaspoons hot water
• 1/2 cup orange juice, warmed
• 1 1/4 teaspoons vanilla extract
• 1/4 teaspoon grated orange peel
• 1/4 teaspoon grated lemon peel
• 1 1/2 cups all-purpose flour
• 1 1/4 teaspoons baking powder
• 1/4 teaspoon salt
• 6 egg whites
• 3/4 cup reduced-fat frozen whipped topping