Prep the marinade: In a large bowl, whisk lemon zest, lemon juice, black pepper, salt, olive oil, garlic, honey, and onion powder until combined.
Marinate the chicken: Add chicken thighs and toss to coat. Cover and refrigerate for 20–60 minutes.
For deeper flavor, marinate up to 6 hours.
Preheat the grill: Heat a gas or charcoal grill to medium-high (425–450°F). Clean and oil the grates to prevent sticking.
Shake off excess: Let extra marinade drip off each thigh to avoid flare-ups.
Grill the chicken: Place thighs on the grill. Cook for 5–6 minutes per side for boneless, or 7–9 minutes per side for bone-in, turning once.
Aim for an internal temperature of 165°F.
Rest and finish: Transfer to a plate and rest for 5 minutes. Squeeze with fresh lemon and sprinkle parsley. Add a pinch more pepper if you love the bite.
Serve: Pair with grilled asparagus, a simple green salad, rice, or roasted potatoes.