Season the fish with salt and let rest for 20 minutes. Preheat the broiler to low and set the rack in the position closest to the heat. Combine panko, parsley, thyme, zests and butter to make a paste. Place fish on a baking dish and cover with breakcrumb mixture, patting it down gently. Place under the broiler and cook until the fish is done and the crust is lightly browned, about 7-10 minutes, depending on thickness.
Nutrition per serving: 320 calories; 18g total fat (11g saturated); 240mg sodium; 6g carbohydrates; 0g dietary fiber; 1g sugar (0g added sugar); 32g protein