If Making Chile Blend: bring a pot of water to a boil and add the chili’s (ancho, guajillo and de arbol). Bring to a boil and boil for 15 mins.
Marinade: To a blender add the boiled chili’s, achiote paste, onion, pineapple juice, vinegar, garlic, salt, Mexican oregano, cinnamon, clove. Blend until pureed.
Trim fat from the pork shoulder and slice meat into 1/4 inch slices. Place pork in a plastic bag that seals or container that can be covered with a lid and pour the chile mixture over the pork. Using gloves, mix the chile marinade and pork then chill in refrigerator, covered, 4 hours or overnight. Allow meat to come to room temp prior to cooking.
Remove all racks except bottom one from oven. Preheat oven to 250°F.
Shake off excess marinade. In a cast iron skillet or baking tray place the cut pineapple bottom(s). Insert a wooden or metal skewer or long wooden chopstick in the center of the pineapple. Start layering pieces of marinated pork, repeating until meat is used, or you have 1 inch of skewer left. Leave 1 inch of skewer on top and cap it with trimmed pineapple top. Slow roast at 250°F for 2 1/2 hours or until meat is cooked (we want an internal temp of 145°F-150°F). Start basting with pan juices in last hour. Outside will be caramelized and crispy, cut with knife in downward motion.
To serve: Serve in small tortillas topped with chopped onion, cilantro, squeeze of lime juice, fresh made guacamole and your favorite hot sauces.