Preheat your oven to 400°F (200°C).
Toss the tomatillos, onion, jalapeños, and unpeeled garlic with olive oil and salt on a baking sheet.
Bake the vegetables until they’re browned on all sides, about 30 minutes.
Remove the skins from the garlic and discard the seeds from the chilis.
In a blender, combine the roasted veggies with water or broth; blend until smooth.
Pour the mixture into a saucepan, bring it to a boil, then reduce the heat and let it simmer for about 10 minutes.
Stir in the cilantro and lime juice, adjusting salt and pepper to taste.
