Roast poblanos, onion, and garlic over a gas flame or under broiler, turning until charred on all sides, about 10–12 minutes.

Place roasted vegetables in a bowl and cover for 10 minutes to steam, then peel skins off poblanos and remove seeds.

Put poblanos, onion, garlic, cilantro, lime juice, salt, pepper, and oil in a blender.

Pulse to a chunky texture, scraping sides once. Taste and adjust salt or lime.

Chill at least 30 minutes before serving to let flavors settle.