Prepare the marinade: In a bowl, combine olive oil, lime juice and zest, chopped cilantro, minced garlic, cumin, chili powder (if using), salt, and pepper. Stir until well mixed.

1. Marinate the chicken: Place the chicken in a resealable plastic bag or shallow dish. Pour the marinade over the chicken, making sure it’s evenly coated. Seal the bag or cover the dish, refrigerate for at least 30 minutes, or up to 4 hours. Marinate overnight for the best flavor.
2. Preheat the grill: Preheat the grill to medium-high heat (about 400°F or 200°C). For a charcoal grill, ensure the coals are hot and evenly spread.
3. Grill the chicken: Remove the chicken from the marinade and discard the marinade. Grill the chicken for 5-7 minutes per side, depending on thickness, or until the internal temperature reaches 165°F (74°C).
4. Rest the chicken: Remove the chicken from the grill and let it rest for about 5 minutes to allow juices to redistribute.
5. Serve: Slice the chicken and serve with a side of rice, grilled vegetables, or in tacos. Garnish with extra cilantro and a wedge of lime for added freshness.