How to Make It
In a small saucepan, combine the chipotles and their sauce with the garlic, orange zest, orange juice, lime juice, red wine vinegar, tomato paste, oregano, cumin and pepper. Simmer over high heat until reduced by one-third, about 3 minutes. Transfer the contents of the pan to a food processor and puree until smooth. Let cool before using.
Coat the pork with 1/4 cup of the marinade and refrigerate for 2 hours.
Light the grill. Grill the pork over a hot fire, turning, until cooked through, about 15 minutes. Let stand for 3 minutes before slicing and serving.