Make the adobo

1. If the pork feels floppy and hard to slice neatly, place it in the freezer for 20 minutes until just firm at the edges. Slice it thinly and set it in a large bowl.
2. Put the guajillo chiles in a heatproof bowl, cover with hot water, and let them soften for 10 minutes. Drain well.
3. In a blender, combine the softened guajillos, achiote paste, orange juice, vinegar, pineapple juice, garlic, oregano, cumin, black pepper, cloves, salt, and oil. Blend until very smooth and thick.

Marinate the pork

1. Pour the adobo over the sliced pork and toss until every piece is thoroughly coated.
2. Cover and refrigerate for at least 2 hours or up to 8 hours. (Optional) Marinate 12 to 24 hours for a deeper, more rounded chile flavor, but use canned or bottled pineapple juice for that longer rest; if using fresh pineapple juice, keep the marinade closer to the 2 to 8 hour range. Keep it refrigerated the entire time.
3. About 20 minutes before cooking, place a rack in the upper third of the oven and preheat to 425°F / 220°C. Line a rimmed baking sheet with parchment or foil.

Roast and serve

1. Choose your cooking method for the marinated pork:
   Oven: Spread the pork and its thick marinade over a lined rimmed baking sheet in an even layer. Scatter 1 cup / 140 g of the pineapple over the top, and reserve the remaining ½ cup / 70 g for serving.
   Charcoal grill: Thread the pork onto skewers or pack it tightly onto 2 double skewers so it stays secure, then grill over medium-high direct heat. Grill 1 cup / 140 g of the pineapple separately in larger pieces or slices, and reserve the remaining ½ cup / 70 g for serving.
   Frying pan: Heat a large skillet or frying pan over medium-high heat with 1 tbsp / 15 ml neutral oil. Cook the pork in 2 to 3 batches so the pan stays hot and the meat sears instead of steaming. Add 1 cup / 140 g of the pineapple to the pan during the last few minutes of the final batch, or cook it separately until lightly browned, and reserve the remaining ½ cup / 70 g for serving.

2. (Optional) Upgrade: Give the pineapple its own little blast of heat for the last couple of minutes instead of treating it exactly like the pork. That extra caramelization makes the sweet-tart contrast pop much more clearly in the finished tacos.

3. Cook until the pork is cooked through and well browned in spots:
   Oven: Roast at 425°F / 220°C for 18 to 24 minutes, stirring once halfway through, then broil for 2 to 4 minutes if you want deeper color and more charred edges.
   Charcoal grill: Grill for about 10 to 14 minutes total, turning every few minutes, until the edges are lightly charred and the pork is cooked through. Grill the pineapple until lightly caramelized, then dice it.
   Frying pan: Cook each batch for about 4 to 6 minutes, stirring occasionally, until browned at the edges and cooked through. Let later batches pick up some darker bits for a more al pastor-style finish.
4. Check the thickest pieces with an instant-read thermometer; the pork should reach at least 145°F / 63°C, then rest for 3 minutes before chopping. While it rests, warm the tortillas in a dry skillet for about 20 seconds per side, then stack and wrap them in a clean towel.
5. Chop the pork into bite-size pieces, toss together with the cooked pineapple, and divide among the tortillas. Top with the reserved ½ cup / 70 g pineapple, the onion, cilantro, and lime. Success looks like juicy pork with red-brown edges, a little sticky char, and a bright sweet-savory balance that still tastes clearly of chile and achiote.