This incredibly unique combination of achiote paste, bitter orange, and deep-flavored pork is a wonderful example of traditional Mayan cuisine. It used to take a day or two to achieve this magnificent mix of flavors and softness, but now this dish can be enjoyed in 1½ hours in today's kitchen. Not bad. No digging pits or burying whole pigs wrapped in banana leaves, either. This a great dish to serve for a party
Make Marinade - To a blender or food processor, add juices, vinegar, achiote paste, oregano, cumin, clove, allspice, pepper, cinnamon, garlic, salt, and ¼ onion. Blend until smooth.
Prepare Pork - Remove any skin and excess fat from pork. Cut into 2 to 3-inch chunks. Put cut pork chunks in 1-2 large plastic freezer bags and add marinade. Seal and massage marinade into each piece. Place in refrigerator for 4 hours up-to overnight.
Cook Pork - Pour the pork and its marinade into the bowl of an Instant Pot. Add bay leaves and layer onion and tomato slices over meat. Lock lid and move valve to "SEALING." Cook on "HIGH PRESSURE" Pressure for 60 minutes. Allow full "NATURAL RELEASE" for 20 minutes then move valve to "MANUAL RELEASE," until pin pops-up. Carefully scoop out pork chunks to a deep bowl with a slotted spoon. Shred pork pieces with 2 forks and moisten (not drown) shredded pork with juices from pot.
To Serve - Put bowls of spicy salsa and pickled red onions next to the bowl of pork. Wrap tortillas in a moistened kitchen towel and put in Microwave for 30 seconds to warm. Bowls of beans Mexican rice round out a great meal.