Place 2/3 of the olive oil, parsley, garlic, lemon zest, and red pepper flakes (if using) in a blender or food processor and pulse until chopped well. Add more zest to taste as desired. Season with salt and pepper to taste and set aside. (Alternatively, mince the ingredients using a knife and whisk well in a bowl).
Preheat a grill pan on medium heat.
Season both sides of the chicken with paprika, salt, and pepper. Drizzle with remaining oil on both sides.
Nicely char grill the chicken on each side to an internal temperature of 160°F using a thermometer (about 3-6 minutes on each side depending on thickness). Once chicken is cooked, set aside and allow to rest for 5 minutes then slice.
Spoon the gremolata over chicken (about 2 tablespoons per portion). Serve with bread.
Notes
Pro tips: Butterfly the chicken: Lay the breasts down on a cutting board, using a sharp knife parallel to the cutting board slice the breasts through the middle (carefully) all the way in half.