How to Make It
In a large bowl, combine the onion with the tomato, bell peppers, olive oil and lemon juice. Add a large pinch each of salt and pepper and mix well. Cover and refrigerate overnight. Stir in the parsley and bring to room temperature before serving.
Light a grill. Season the lamb and short ribs with salt and pepper and let stand for 10 minutes. Grill all of the meats over moderate heat, turning occasionally, until the short ribs are browned and cooked through, about 12 minutes; the chorizo is cooked through, about 15 minutes; and an instant-read thermometer inserted in the thickest part of the lamb registers 130° for medium-rare, 25 to 35 minutes, depending on thickness. Transfer the meats to a platter to rest for 5 minutes.
Season the salsa once more with salt and pepper. Carve the grilled meats and serve the salsa alongside.