Copycat Chipotle Chicken

Place onion, chipotles, lime juice, garlic, cumin, oregano, salt and pepper in a food processor. Process until mostly smooth and well combined, 30 seconds to 1 minute. 

Transfer the marinade to a large zip-top plastic bag; add chicken. Seal the bag and refrigerate for at least 3 hours or up to 12 hours.  

Let the chicken stand at room temperature while preparing pan. Heat a grill pan over medium-high heat. (Alternatively, preheat grill to medium-high heat. Lightly coat the grill pan with cooking spray and place on grates. Do not use cooking spray over open flames.) Remove the chicken from the marinade (discard any remaining marinade). Coat the grill pan lightly with cooking spray. Cook the chicken, turning halfway, until lightly charred and cooked through, about 6 minutes.