Gather the ingredients and grease a shallow baking dish. Preheat oven to 325 degrees.
Cut the flounder fillets into serving-size portions, or serve whole filets if seem to be the correct size. Arrange the pieces into a prepared baking dish or baking sheet, and sprinkle with salt and freshly ground black pepper.
In a small bowl combine melted butter, lemon juice, and small diced onion. Pour the lemon-butter mixture over the fish.
Sprinkle the fish with paprika and bake in the preheated oven for 15 to 25 minutes, depending on the thickness of the fillets, or until the fish is cooked through and flakes easily with a fork.
Garnish with chopped parsley, lemon wedges, and serve!
Notes
*Thanks to Brian and Lily for catching the flounder today :)