Discard husks and stems from tomatillos; cut into quarters. Place tomatillos, 1 1/2 cups water, salt, and peppers in a large saucepan; bring to a boil. Cover, reduce heat, and simmer 15 minutes, stirring occasionally. Cool.
Transfer tomatillo mixture to a food processor, and process until smooth. Add cilantro, and pulse 5 times or until blended.