Turn on a gas grill to medium or light a charcoal fire, letting the coals burn until they are covered with a gray ash and are medium-hot. If you have wide grates, place a perforated grill pan over the grates. Lay the tomatoes, onion, garlic and chile directly over the fire and grill, turning occasionally, until everything is soft and blackened in spots—about 10 minutes for the garlic, 15 minutes for the chile and 20 minutes for the tomatoes and onions. Cool all the vegetables until handleable, then peel the tomatoes and garlic. Roughly chop them along with the onion, scoop into a food processor and process into a coarse puree. Transfer to a serving bowl. Peel the chiles and pull out the stem, then rinse briefly to remove all the seeds and bits of skin. Slice into 1/8” strips and stir into the salsa along with the lime juice and cilantro. Taste and season with salt, about 1 teaspoon. If the salsa is too thick, drizzle in a little water.