Grind annatto seeds, then combine in a blender with the coriander, oregano, cumin, black pepper, salt, cloves, garlic, orange juice, and lime juice. Pulse until a thick paste forms. Score the top of the pork butt with a sharp knife, then coat the pork with the achiote paste mixture and place, covered, in the fridge for a minimum of 4 hours to marinate.
Preheat Cuisinart Twin Oaks Pellet & Gas Grill to 200 degrees on the pellet side. Once hot, place the marinated pork butt in the center of the grill, insert a meat probe into the center of the thickest portion, then close the lid and let smoke until the probe reads a temperature of 165 degrees.
Turn the smoker up to 250 degrees and allow the pork to continue cooking, without lifting the cover, until the probe reads 215 degrees. Remove from the smoker and let sit for 30-60 minutes uncovered before shredding. Serve with tortillas, salsa verde, and pickled red onions, or your favorite taco fixings and enjoy!