In a large, unoiled frying pan over medium heat, pan-roast the Jalapeños, onion, garlic, and tomatillo on all sides, 20 to 25 minutes total.
In a blender, whirl the vegetables with 1/4 cup water until blended but still chunky. Add avocado and lime juice; pulse until blended. Add cilantro and salt, pulse to combine, and add more salt and/or lime juice to taste.
Note: Nutritional analysis is per tablespoon.