Make the fish marinade by combining the olive oil, dill, garlic, and zest in a large zip-lock bag, and mix well. Add the fish, coating the filets in the marinade.
Marinate in the refrigerator for 2-4 hours. Side Note: Do not add lemon juice to the marinade; the acid in the lemon will start to cook the fish.
Preheat the oven to 450 degrees. Coat a large baking dish with butter or cooking spray.
Place the fish in the baking dish and drizzle the lemon juice all over each filet, and top each with a tablespoon of butter.
Cook the fish by placing it in the oven and bake for 7-10 minutes, until it flakes easily.