For the sauce
3 tablespoons canola or vegetable oil
1 tablespoon achiote (annatto) seeds
1/2 cup red wine vinegar
5 garlic cloves, finely minced
1 tablespoon seeded and finely chopped canned aji amarillo peppers (or 1 tablespoon finely chopped roasted red or yellow peppers plus 1/4 teaspoon cayenne pepper)
2 teaspoons ground cumin
2 teaspoons salt, plus extra for the skewers
2 teaspoons freshly ground pepper, plus extra for the skewers
For the pork
1 pineapple, peeled, cored, and cut into 1-inch cubes
1 pound pork loin, cut into 1-inch cubes
1 large red onion, quartered, then halved widthwise
1 head of butterhead lettuce (such as Bibb or Boston)
Lime wedges, for serving
- Heat the oil in a small saucepan over medium-high heat and add the achiote seeds. Turn off the heat and let the seeds steep until the oil turns a vibrant orange-red, about 5 minutes. Strain the oil through a fine-mesh sieve and discard the seeds. Place the achiote oil in a blender along with the vinegar, garlic, aji amarillo, cumin, salt, and pepper and purée the mixture.
- Place the pork in a resealable gallon-sized plastic bag. Add the achiote marinade, turn the bag to coat the pork, and refrigerate for at least 4 hours or overnight.
- Preheat your grill to high heat. Thread the pork onto skewers alternately with the pineapple and red onion. Sprinkle the skewers with a little salt and pepper. Grill until browned on all sides, 4 to 6 minutes total; don’t overcook or the pork will be tough and dry. Serve the skewers on a bed of lettuce leaves with some lime wedges.