Clean the flounder, cut off the head, fins and tail. Rub the fish with salt and pepper to taste.
Cut the bulbs into thick rings.
In warmed vegetable oil, fry half the onion until golden, salt and pepper it a little. Then put it on a napkin to remove fat.
Fry the flounder in the same pan where the onion was for 3 minutes on each side, put a little onion next to the fish so that it removes the smell.
Then replace the onion with fresh and cook the fish until golden brown.
Serve the flounder laying it on the fried onion.