01 - In a medium bowl, whisk together olive oil, lime juice, lime zest, garlic, chili powder, cumin, smoked paprika, cayenne (if using), salt, and black pepper until well combined.
02 - Place chicken breasts in a large resealable plastic bag or shallow dish. Pour marinade over the chicken, ensuring all pieces are well coated. Seal and marinate in the refrigerator for at least 30 minutes, up to 2 hours for more flavor.
03 - Preheat grill to medium-high heat, approximately 400°F.
04 - Remove chicken from marinade and let excess drip off. Discard leftover marinade.
05 - Grill chicken breasts for 6–8 minutes per side, or until cooked through and internal temperature reaches 165°F.
06 - Transfer chicken to a plate, cover loosely with foil, and let rest for 5 minutes to allow juices to redistribute.
07 - Slice and serve garnished with chopped cilantro and lime wedges.