01 - Preheat the oven to 400°F. Lightly grease a baking dish with olive oil.
02 - In a small bowl, whisk together lemon zest, lemon juice, dill, garlic, Dijon mustard, onion powder, and red pepper flakes until well combined.
03 - Pat the chicken breasts dry with paper towels. Rub them evenly with olive oil, sea salt, and black pepper. Place in the prepared baking dish.
04 - Pour the marinade evenly over the chicken breasts, turning to coat thoroughly. Let sit at room temperature for at least 10 minutes, or refrigerate up to 2 hours for deeper flavor.
05 - Bake uncovered for 25 to 30 minutes, or until the chicken is cooked through and juices run clear. The internal temperature should reach 165°F.
06 - Remove from oven and let the chicken rest for 5 minutes before serving. Garnish with additional fresh dill and lemon slices.