Martha Stewart, a magazine editor, star of her own television show and author of the popluar "Weddings" book joins Julia to bake one grand a nd glorious three-tiered wedding cake. Martha prepares the batter and bakes each layer in graduated diamond-shaped cake forms. While the cak e bakes, and then chills, Martha creates a variety of delicately reali stic and delicious marzipan fruits, right down to the little stems and leaves. She also makes and chills enough vanilla rum buttercream to i ce the entire cake.