Place the tomato on the griddle, stem end down. (Started this way it will lose less juice.) Cook, turning frequently, until the skin is blackened and blistered all over, 15 to 20 minutes. Transfer to a bowl that will hold the juices. At the same time, roast the tomatillos in their husks, turning frequently to guard against scorching, until they are lightly softened all over, 10 to 15 minutes. Handle them delicately so as not to squeeze them and pierce the skins. Carefully transfer them to a bowl to catch the juices. When cool enough to handle, peel the tomato and remove the husks from the tomatillos.