"Brooklyn-based pastry chef Emily Lael Aumiller sits squarely in the overlap of show-stopping cakes and special-needs diets. Her creations are vegan and gluten free, yet look like they belong in a magazine - as indeed they have (see Martha Stewart Weddings and Brides). Her new book, "Pure Artistry: Extraordinary Vegan & Gluten-Free Cakes" (Houghton Mifflin Harcourt, $35), provides a master class in special-diet cakes and cake-decorating. With beautiful...