Baked Flounder With Lemon and Butter

Prep: 15 mins
Cook: 25 mins
Total: 40 mins
Servings: 4 servings

Flounder is a mild white saltwater fish that is delicious when baked. The flatfish is relatively low in mercury, making it safe for children and pregnant women. Fillets can be purchased at the fish market or bought frozen. Both will work for this recipe. If your flounder fillets are frozen, defrost them in the refrigerator overnight before using.

Baked flounder fillets with chopped parsley and lemon wedges in a baking dish

​The Spruce Eats / Ulyana Verbytska

Adding Flavor to Mild Fish Fillets

This recipe adds lots of flavor with lemon, paprika, and butter while still highlighting the fish's mild taste. As the fish bakes, you'll have just enough time to whip up the optional rich aioli sauce and side dishes like potatoes, rice, green beans, or a lightly dressed salad. If you feel like skipping the aioli, flounder is especially good when served with a store-bought tartar sauce or pesto instead. 

Flounder Alternatives

The recipe can be made with sole, haddock, cod, or another mild white fish. Adjust the baking time if the fillets are thick; they may take a little longer.

Tips for Preparing Fish

  • Don't overcook—Fish can quickly become tough and dry if overcooked in the oven. If the fillets are very thin, check for doneness after about 10 minutes.
  • Longer baking time—Thicker cuts of fish may take longer than 25 minutes to cook through. Check the fillets after 15 minutes to prevent overcooking.
  • Use the pan sauce—Don't leave the pan sauce behind! It's delicious and will help keep the fish moist.

"This is the perfect weeknight fish recipe. Flounder is a delicious, mild white fish that takes on the flavor of what it’s cooked in, so the final product is light and goes great with the garlic aioli. If you are looking for a recipe for the fish-adverse, I would highly recommend this one." —Tracy Wilk

Baked Flounder With Lemon and Butter Tester Image
A Note From Our Recipe Tester

Ingredients

For the Fish

  • 1/4 cup melted unsalted butter, plus solid butter for the baking dish

  • 1 1/2 pounds flounder fillets

  • 1 teaspoon fine salt, or to taste

  • 1/8 teaspoon freshly ground black pepper

  • 2 tablespoons freshly squeezed lemon juice, plus slices or wedges for serving

  • 2 teaspoons minced onion

  • 1 teaspoon paprika

  • 1 tablespoon finely chopped parsley, for garnish

For the Optional Garlic Aioli

  • 2 medium cloves garlic

  • 1/2 cup mayonnaise

  • 2 tablespoons olive oil

  • 1 tablespoon freshly squeezed lemon juice

  • Fine salt, to taste

Steps to Make It

Make the Fish

  1. Gather the ingredients.

    Ingredients for baked flounder recipe with lemon and butter gathered

    ​The Spruce Eats / Ulyana Verbytska

  2. Grease a shallow baking dish with the solid butter. Position a rack in the center of the oven and heat to 325 F/165 C.

    Shallow ceramic baking dish greased with butter

    ​The Spruce Eats / Ulyana Verbytska

  3. Cut 1 1/2 pounds flounder fillets into 4 same-size portions. 

    Flounder fillets placed on paper towels and cut into serving-size portions with a large knife

    ​The Spruce Eats / Ulyana Verbytska 

  4. Arrange the pieces in the prepared baking dish, and sprinkle with 1 teaspoon fine salt, or to taste, and 1/8 teaspoon freshly ground black pepper.

    Flounder pieces arranged in baking dish in a single layer and sprinkled with salt and black pepper

    ​The Spruce Eats / Ulyana Verbytska

  5. In a small bowl or measuring cup, combine the remaining 1/4 cup melted unsalted butter, 2 tablespoons freshly squeezed lemon juice, and 2 teaspoons minced onion.

    Melted butter, lemon juice, and minced onion combined in a small spouted bowl and stirred with a spoon

    ​The Spruce Eats / Ulyana Verbytska

  6. Pour the lemon-butter mixture over fish.

    Melted butter mixture being poured over the flounder pieces in baking dish

    ​The Spruce Eats / Ulyana Verbytska

  7. Sprinkle with 1 teaspoon paprika.

    Paprika being sprinkled over the flounder in the baking dish

    ​The Spruce Eats / Ulyana Verbytska

  8. Bake until the fish is cooked through and flakes easily with a fork, 15 to 25 minutes, depending on the thickness of the fillets. Meanwhile, make the garlic aioli, if desired.

    Baked flounder being tested for flakiness with a fork

    ​The Spruce Eats / Ulyana Verbytska

  9. Garnish with 1 tablespoon finely chopped parsley and lemon slices or wedges. Serve with garlic aioli, if using.

    Baked flounder with chopped parsley and lemon wedges in a baking dish

    ​The Spruce Eats / Ulyana Verbytska

Make the Optional Garlic Aioli

  1. Gather the ingredients.

    Ingredients for garlic aioli recipe gathered

    ​The Spruce Eats / Ulyana Verbytska

  2. Crush 2 medium cloves garlic, transfer to a medium bowl, and mash well with a fork. Alternatively, use a mortar and pestle.

    Garlic being mashed with a fork in a glass bowl

    ​The Spruce Eats / Ulyana Verbytska

  3. Add 1/2 cup mayonnaise, 2 tablespoons olive oil, and 1 tablespoon freshly squeezed lemon juice to the bowl. Stir well to blend.

    Mayonnaise, olive oil, and lemon juice being added to garlic and stirred with a fork

    ​The Spruce Eats / Ulyana Verbytska

  4. Season with fine salt, to taste.

    Salt being added to the aioli

    ​The Spruce Eats / Ulyana Verbytska

  5. Cover and chill until serving time.

    Aioli in glass bowl covered with plastic wrap until ready to serve

    ​The Spruce Eats / Ulyana Verbytska

Feeling Adventurous? Try This:

Play with your food—Experiment with other herb combinations, either fresh or dried. If using dried, cut the quantity in half since dried herbs are more powerful than fresh. Here are some herb suggestions to play with: Chives, sage, dill, basil, tarragon, or rosemary.

How to Store

If you have leftovers, it's best to get them into the refrigerator as soon as possible. Keep the fish wrapped tightly or in a sealed container and it should be good for about 3 to 4 days.

Nutrition Facts (per serving)
502 Calories
43g Fat
2g Carbs
27g Protein
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Nutrition Facts
Servings: 4
Amount per serving
Calories 502
% Daily Value*
Total Fat 43g 55%
Saturated Fat 12g 61%
Cholesterol 137mg 46%
Sodium 1472mg 64%
Total Carbohydrate 2g 1%
Dietary Fiber 0g 1%
Total Sugars 1g
Protein 27g
Vitamin C 3mg 17%
Calcium 56mg 4%
Iron 1mg 4%
Potassium 386mg 8%
*The % Daily Value (DV) tells you how much a nutrient in a food serving contributes to a daily diet. 2,000 calories a day is used for general nutrition advice.
(Nutrition information is calculated using an ingredient database and should be considered an estimate.)