Prep time: 15-20 minutes Cook time: 15-17 minutes Rest time: 3-5 hours Sponge Cake Materials: 8 eggs separated into whites and yolks 8 tbsp. sugar 1 tbsp. water 10 tbsp. all-purpose flour sifted 4 tbsp. potato starch sifted Non-stick cooking spray Rhubarb Layer Materials: 2 lbs rhubarb cut into 1 inch pieces 1/2 cup sugar…