Red onions are colorful with a spicy-to-mild flavor. Because of their bright color and crispy texture, they're great for adding crunch and punch to sandwiches, salads, and burgers. Relish them raw? They also add a mellow moistness and flavor to guacamole, salsas, frittatas, pasta primavera, and stir-fries. It's hard to imagine a summer kitchen without a basket of these purplish-red beauties.