1 tablespoon canola oil, plus more for brushing
3 garlic cloves
1 teaspoon dried oregano
1/2 teaspoon ground cumin
1/2 teaspoon pepper
1/4 teaspoon ground cloves
4 guajillo chiles—stemmed, seeded and cut into 2-inch pieces
1/3 cup pineapple juice
1/4 cup distilled white vinegar
2 tablespoons achiote paste
2 pounds boneless pork shoulder, sliced 1/4 inch thick
1/2 medium pineapple, peeled and sliced 1/2 inch thick
1 medium red onion, sliced crosswise 1/2 inch thick
Warm corn tortillas, chopped cilantro and lime wedges, for serving
In a medium saucepan, heat the 1 tablespoon of oil. Add the garlic and cook over moderately high heat, turning occasionally, until lightly browned, about 1 minute. Stir in the oregano, cumin, pepper and cloves and cook until fragrant, about 1 minute. Add the chiles and cook, stirring, until blistered in spots, about 30 seconds. Add the pineapple juice, vinegar and achiote paste and bring to a boil. Remove from the heat and let stand for 5 minutes.
Transfer the chile mixture to a blender and puree until smooth. Season with salt. Scrape the marinade into
a large, sturdy plastic bag.
Add the pork and turn to coat. Set the bag in a small baking dish and refrigerate overnight.
Light a grill or preheat a grill pan. Brush the pineapple and onion with oil. Grill over high heat, turning once, until lightly charred and softened, 3 to 5 minutes. Transfer to a carving board and tent with foil.
Remove the pork from the marinade. Grill over high heat until lightly charred and just cooked through, 2 to 4 minutes. Transfer to the carving board and let rest for 5 minutes.
Cut the pineapple, onion and pork into thin strips and transfer to a bowl. Season with salt. Serve with corn tortillas, chopped cilantro and lime wedges.