In a medium bowl, combine chopped fresh cilantro, extra virgin olive oil, lime zest, freshly squeezed lime juice, chili powder, ground cumin, kosher salt, and freshly ground black pepper. Whisk together until well blended.

Place the boneless, skinless chicken thighs into a large Ziploc bag or a bowl, then pour the cilantro lime marinade over them. Seal the bag or cover the bowl and let it marinate in the refrigerator for at least 2 hours, ideally overnight.

After marinating, remove the chicken from the fridge and drain away the excess marinade. Heat extra virgin olive oil in a cast-iron grill pan over medium-high heat.

Add the marinated chicken thighs in a single layer to the hot grill pan. Cook each thigh for 4-5 minutes without moving them, then flip to cook the other side until golden and the internal temperature reaches 165°F.

Once the chicken thighs are cooked, transfer them to a plate and let them rest for at least 5 minutes to allow the juices to redistribute before serving.