A 3-ounce serving of a cooked flounder fillet is high in protein, low in fat and rich in essential nutrients like vitamin B-12, vitamin D and selenium. It is also a good source of the omega-3 fatty acids that may be linked to a decreased risk of heart disease and high blood cholesterol. According to "New York Times" food writer and "How to Cook Everything" author Mark Bittman, flounder has thin fillets that are too delicate to be grilled or poached without the fish falling apart. The best -- and healthiest -- cooking methods for flounder fillets include broiling and baking.
Coat a broiler pan with cooking spray or brush it lightly with oil. Place the flounder fillet on the pan skin-side down if the skin is intact.
Brush the fillet with a small amount of olive oil. Sprinkle the flounder with your choice of seasonings, such as salt, pepper, minced garlic, dill, thyme, rosemary, parsley, basil or lemon juice.
Position your oven rack so that the broiler pan containing the flounder fillet will be as close to the heating element as possible. Preheat the broiler.
Broil the flounder, planning on approximately 3 minutes of cooking time for a fillet that is 1/4 inch thick. Remove the broiler pan from the oven and use a fork to check that the edges of the fillet flakes while the center is still slightly translucent.
Coat a rimmed baking sheet or glass dish with cooking spray or a thin film of oil. Put the flounder fillet into the center of the dish.
Coat the fillet with olive oil using a pastry brush and a light touch. Add whatever seasonings you prefer to the top of the flounder.
Place the flounder in an oven preheated to 450 degrees Fahrenheit. Plan on baking a 1/4-inch-thick fillet for approximately four to five minutes, or until the fillet edges flake while the center is still mildly resistant. Serve right away.