In a mixing bowl, combine the olive oil, orange juice, lime juice, chopped onion, minced garlic, and achiote paste. Whisk until the mixture is well combined and the achiote paste is fully dissolved.
To the marinade, add the ground coriander, ground cumin, kosher salt, smoked paprika, dried oregano, black pepper, and chipotle chile pepper (if using). Mix thoroughly to ensure all the spices are evenly distributed.
Place the bone-in chicken thighs in a large resealable bag or a baking dish. Pour the marinade over the chicken, ensuring each piece is well coated. Seal the bag or cover the dish with plastic wrap, and refrigerate for at least 2 hours, or overnight for maximum flavor.
When you’re ready to cook, preheat your oven to 400°F (200°C). This temperature will help achieve a beautiful caramelization on the chicken.
Remove the chicken from the marinade and place it in a baking dish or roasting pan, skin side up. Pour any remaining marinade over the chicken. Bake in the preheated oven for 35-45 minutes, or until the chicken reaches an internal temperature of 165°F (75°C).
Once cooked, remove the chicken from the oven and let it rest for 5-10 minutes. This helps retain the juices. Serve your Chicken Asado with rice, tortillas, or a fresh salad, garnished with lime wedges and cilantro if desired.