Heat oil in frying pan. Slice onion thinly while it heats, Saute onion until soft.

Raise heat to high. Place salmon fillets, skin side down in pan to sear, then lower heat. Sprinkle dill over the fish, and gently rub it in. Cook about 3 minutes.

Turn fish over. Sprinkle vinegar over it and in pan. Let cook until done to your taste - usually another 4-6 minutes.

Serve at once.