Preheat broiler. On a broiler-proof sheet pan, toss tomatoes with onion, oil, salt, and pepper. Broil until charred in spots, 15 to 20 minutes; cool.
Transfer contents of sheet pan to a food processor; add chipotles, cilantro, and lime juice. Pulse until combined but still chunky.
This salsa is perfect. The smokiness of the roasted tomatoes with the richness and spice of the chipotles is perfect. This is my staple salsa recipe now.
This is a wonderful salsa and very versatile. I usually double to keep one recipe chunkier for salsa and puree then cook the other portion for huevos rancheros.