Prepare the Chicken:
In a small bowl, mix olive oil, garlic powder, smoked paprika, salt, and black pepper. Rub this mixture evenly over the chicken breasts. Let the chicken marinate for 15–20 minutes while you prepare the chimichurri sauce.
Make the Chimichurri Sauce:
In a medium bowl, combine parsley, cilantro (if using), garlic, olive oil, red wine vinegar, red pepper flakes, salt, and black pepper. Stir well and set aside to let the flavors meld.
Grill the Chicken:
Preheat your grill or grill pan to medium-high heat. Place the chicken breasts on the grill and cook for 6–8 minutes per side, or until the internal temperature reaches 165°F (75°C). Remove the chicken from the grill and let it rest for 5 minutes.
Serve:
Slice the grilled chicken breasts and drizzle generously with the chimichurri sauce. Serve with your favorite side dishes like roasted vegetables, rice, or a fresh salad.