Rehydrate dried guajillo and ancho chiles by simmering them in hot water for 15-20 minutes until softened. Drain, reserving some liquid.

In a blender, combine rehydrated chiles, apple cider vinegar, achiote paste, orange juice, minced garlic, ground cumin, dried oregano, black pepper, and salt. Blend until smooth, adding a little reserved chile water if needed for consistency.

Place thinly sliced pork shoulder in a large bowl or resealable bag. Pour the al pastor marinade over the pork, ensuring all slices are well coated. Marinate in the refrigerator for at least 4 hours, or preferably overnight (12-24 hours).

If using a vertical skewer (trompo), slice off the bottom and top of a half onion to create flat surfaces. Secure the onion base on the skewer.

Slide the marinated pork slices onto the vertical skewer, layering them tightly. Alternate with slices of fresh pineapple every few layers. Top the stack with a pineapple ring or another onion half.

Cook on a vertical rotisserie or skewer over indirect heat for 2 to 3 hours, or until the pork is tender and well-caramelized on the outside. Periodically shave off the crispy outer layers as they cook, letting the inner layers continue to cook.

Once cooked, finely chop the shaved pork and pineapple. Serve immediately in warm tortillas with desired toppings like cilantro, onion, and lime.