Blend the Marinade: Start by adding orange juice, lime juice, achiote powder, onion powder, oregano, cumin, black pepper, salt, garlic, vegetable oil, and grapeseed oil into a blender. Blend until smooth and deep red. The mixture should smell bright and earthy with a slight tang from the citrus.
Prepare the Chicken: Place the chicken thighs in a large bowl or zip bag. Trim excess fat if needed so the marinade coats evenly. This step helps the flavors soak in better and keeps cooking consistent.
Marinate Thoroughly: Pour the marinade over the chicken and massage it into every piece. Make sure all sides stay coated. Cover and refrigerate for at least 2 hours. Overnight works even better for deeper flavor.
Bring Chicken to Room Temperature: Before cooking, let the chicken sit out for about 20 minutes. This helps it cook evenly and keeps the meat juicy inside.
Cook the Chicken: Heat a grill pan or skillet over medium heat. Add a light brush of oil. Place chicken in a single layer and cook for about 6 to 7 minutes per side. Look for charred edges and caramelized color.
Rest the Chicken: Once cooked through, transfer the chicken to a plate and let it rest for 5 minutes. This keeps the juices locked in and improves texture.
Slice or Serve Whole: Slice the chicken for tacos or serve whole for plates. Spoon any pan juices over the top for extra flavor.
