Heat a dry comal or flat iron griddle over moderately low heat until hot and pan roast tomatoes and habaneros, turning them occasionally to ensure even roasting, until browned and soft throughout, 25 to 30 minutes. Discard tomato stems and wearing rubber gloves, stem and seed chiles.
In a blender purée tomatoes, chiles, water, and salt until smooth. (Salsa may be made 10 hours ahead and chilled, covered. Bring salsa to room temperature before serving.)
Makes about 1 cup.