Put onion, fresh chile, tomatillos, and garlic on a baking sheet. Broil 4 to 5 in. from heat, turning once, until blackened, 8 to 10 minutes total. Let cool.
Peel, stem, and seed fresh chile and cut into chunks. In a blender or food processor, whirl broiled onion, chile, tomatillos, garlic, chipotle chiles with sauce, cilantro, and lime juice until coarsely puréed. Season to taste with salt.
Note: Nutritional analysis is per serving.