Clean fish fillets. Season with salt (only if not using capers, otherwise it will be too salty), black pepper, garlic and onion powder. Add paprika and oregano.
Spray air fryer basket with oil. Lay sliced lemon in the basket. Place seasoned flounder fillets on top of lemon. Place capers on top along with butter (if using)
Cook at 375 degrees for 7 minutes.
Notes
Do not overcrowded the air fryer basket.
If unsure that the fish is cooked all the way,check its internal temperature. It should be at least 145 degrees Fahrenheit in the thickest part.
Again, do not use salt if adding capers. Capers are very salty and fillets will be too salty if added both capers and salt.
To prevent fish from sticking lay the air fryer basket with sliced lemon. Additionally it will infuse fish with some lemon flavor. Or you can use air fryer liners.