1. Prepare the marinade: In a blender, combine achiote paste, chipotle peppers in adobo, orange juice, pineapple juice, white vinegar, minced garlic, dried oregano, ground cumin, salt, and black pepper. Blend until very smooth.

2. Marinate the pork: Place the thinly sliced pork shoulder in a large bowl or a resealable plastic bag. Pour the prepared marinade over the pork, ensuring all pieces are thoroughly coated. Refrigerate for at least 4 hours, or preferably overnight, to allow the flavors to penetrate.

3. Cook the pork: Heat a large heavy-bottomed skillet or grill pan over medium-high heat. If using a skillet, you may add a tablespoon of oil. Cook the marinated pork in batches, without overcrowding the pan. Cook until the pork is nicely browned and cooked through, about 3-5 minutes per side. For an extra touch, you can add some diced pineapple to the pan during the last few minutes of cooking with the pork, letting it caramelize slightly.

4. Warm the tortillas: While the pork is cooking, warm the corn tortillas. You can do this on a dry skillet over medium heat for about 15-20 seconds per side, or wrap them in a damp paper towel and microwave for 30-60 seconds until soft and pliable.

5. Assemble the tacos: Spoon a generous amount of the cooked al pastor pork onto each warm tortilla. Top with a sprinkle of diced fresh pineapple, finely diced white onion, and chopped fresh cilantro.

6. Serve immediately: Serve your Tacos al Pastor with fresh lime wedges on the side for squeezing and your favorite salsa for an extra kick.