Prepare Marinade: Blend rehydrated chilies, achiote, garlic, pineapple juice, vinegar, cumin, oregano, and salt until smooth.
Marinate the Pork: Coat pork slices with marinade. Cover and refrigerate for at least 4 hours (overnight preferred).
Cook the Meat: Traditionally, stack pork slices on a vertical spit with pineapple on top and roast. At home: grill or roast slices until charred and cooked through.
Assemble Tacos: Warm corn tortillas. Add sliced pork, top with pineapple, onion, cilantro, and salsa.
Serve: Eat hot with lime wedges for extra zest.