Wrap eggplant in a double layer of aluminum foil, sealing the package well. Set package directly over a medium gas flame or a charcoal fire, turning occasionally until eggplant is tender, about 25 minutes. You can also bake the eggplant unwrapped on a baking sheet in a moderately hot oven, about 400 degrees, pricking it first to prevent bursting, but it will not have the desirable smoky taste.