Begin by flattening the boneless skinless chicken breast. Place it between two sheets of plastic wrap or parchment paper and gently pound it to an even thickness using a meat mallet or rolling pin.
In a medium bowl, combine the olive oil, lemon juice, fresh chopped cilantro, salt, pepper, garlic powder, and crushed red pepper flakes. Whisk together until well blended. Add the chicken breast to the marinade, ensuring it is evenly coated. Allow it to marinate for at least 15 minutes, or up to 2 hours in the refrigerator.
Heat the skillet over medium-high heat and add the avocado oil (or olive oil if you prefer). Let the oil heat until shimmering, but not smoking.
Carefully place the marinated chicken in the hot skillet. Allow it to cook for about 6-7 minutes on one side without moving it.
Using tongs, flip the chicken breast over and reduce the heat to medium. Cook for an additional 6-7 minutes, or until the internal temperature reaches 165°F (75°C).
Once cooked, remove the chicken from the skillet and let it rest for a few minutes. Garnish with extra fresh chopped cilantro before slicing.