Made from a blend of spices that includes oregano, cumin, clove, cinnamon, black pepper, allspice, and garlic, achiote paste (also known as recado rojo) is the focal point of flavor in these tacos. Serve with a bright and spicy pineapple-cilantro salsa to balance out the rich, deep spices of the chicken.
Combine the olive oil, achiote paste, ¼ cup lime juice, spices, and garlic in a small food processor, or by hand with a fork in a small bowl, until smooth. In a ziplock bag or large bowl, toss it with the chicken thighs to coat completely. Marinate at room temperature for at least 30 minutes or covered in the refrigerator overnight.
About 30 minutes before you cook the chicken, make the salsa: Remove the top of the pineapple, trim away the sides, and cut the fruit away from the core. Finely chop it—you only need 1 ½ cup’s worth—and combine it with the cilantro, onion, jalapeño, lime zest, and ½ teaspoon salt. Separately, combine the crema with the remaining 2 Tbsp lime juice. Set both aside.
Heat the vegetable oil in a large cast iron or nonstick skillet over medium-high heat. When the oil is shimmering, pull the chicken out of the marinade, and season it all over with about ¼ teaspoon salt to each piece. Cook in a single layer, working in batches so you don’t overcrowd the pan, for 5 to 6 minutes, until it’s nicely browned; flip, and cook for another 4 or 5 minutes, until it’s cooked through. Repeat with the remaining chicken. Allow to rest for a few minutes, then thinly slice.
Set each tortilla directly over a burner on medium-high heat, and toast for 1 or 2 minutes per side, until lightly charred. Add the chicken to the tortillas, and then top with the pineapple-cilantro salsa.