1 pound green tomatoes
2 to 3 jalapeño or serrano peppers (more to taste)
1/2 medium onion, preferably a white onion, chopped, soaked for five minutes in cold water, drained, rinsed and drained again on paper towels
Salt to taste
1/2 cup roughly chopped cilantro
1/4 to 1/2 cup water, as needed (optional)
Preheat the broiler. Line a baking sheet with foil. Place the green tomatoes on the baking sheet, stem-side down, and place under the broiler about 2 inches from the heat. Broil two to five minutes, until charred. Using tongs, turn the tomatoes over, and grill on the other side for two to five minutes, until blackened. Remove from the heat. When cool enough to handle, core the tomatoes and remove the charred skin. Quarter and place in a blender or a food processor fitted with a steel blade (I prefer the blender).
Add the remaining ingredients, except the water, to the blender or food processor, and blend to a coarse or a smooth puree (to your taste). Transfer to a bowl, taste and adjust seasonings, and thin out with water if desired. Allow to stand for 30 minutes or longer before serving to allow the flavors to develop. You may wish to thin out after it stands.