In a blender or food processor, combine onion, garlic, achiote paste, sour orange juice, cumin, oregano, cinnamon, cloves, olive oil, salt and pepper. Blend until smooth.
Put the pork shoulder in a large bowl and pour the marinade over it. Mix well to coat the pork.
Cover and refrigerate for at least 2 hours or overnight.
Preheat oven to 350°F. Place the pork and marinade in a roasting pan.
Bake, uncovered, for 2-3 hours, or until the meat is fork-tender.
Remove the pork from the oven and let it cool slightly. Use two forks to shred the pork.
Serve the pork in tacos, burritos, or as a main dish.
Interesting Facts
Cochinita Pibil is a traditional dish from the Yucatan region of Mexico.
The marinade for this dish is made with achiote paste, which is made from annatto seeds and is a common ingredient in Mexican cuisine.
The pork is slow-roasted in the oven for a tender, flavorful result.