In a large bowl, whisk together honey, lime juice, olive oil, minced garlic, cumin, chili powder, salt, black pepper, and cayenne pepper (if using) until well combined.
Add the chicken breasts to the marinade, ensuring they are fully coated. Cover the bowl with plastic wrap and refrigerate for at least 1 hour, or up to 4 hours for more flavor.
Preheat the grill to medium-high heat.
Remove the chicken from the marinade and discard the leftover marinade.
Grill the chicken for about 6-7 minutes per side, or until the internal temperature reaches 165°F and the chicken is cooked through.
Remove the chicken from the grill and let it rest for 5 minutes before slicing.
Garnish with chopped cilantro before serving.