In a mixing bowl, combine the salt, ground black pepper, coriander, paprika, cumin, and cayenne pepper. Add the minced red onion and garlic for an aromatic kick. Then, mix in the Harissa paste, fresh lemon juice, and olive oil until well blended.
Place the boneless, skinless chicken breasts into a large resealable plastic bag or a shallow dish. Pour the marinade over the chicken, ensuring each piece is well coated. Seal the bag or cover the dish and refrigerate for at least 30 minutes, or preferably overnight for maximum flavor.
Preheat your skillet or grill over medium-high heat. Remove the chicken from the marinade, allowing any excess to drip off. Cook the chicken for about 6-7 minutes on each side, or until the internal temperature reaches 165°F (75°C). The chicken should have a beautiful char and be cooked through.
Once cooked, let the chicken rest for a few minutes before slicing. Serve it alongside your favorite sides, or slice it to top a salad or in a wrap.
