1) In a heavy-duty, resealable plastic bag, combine oil, lemon juice, garlic, Worcestershire sauce, and pepper; add steaks to bag. Press the air out of the bag and seal tightly. Turn the bag several times to distribute the marinade. Place the bag in a bowl and refrigerate 30 minutes, turning bag occasionally.
2) Heat a large skillet over medium-high heat. Remove steaks from marinade, discarding marinade. Place 3 steaks in hot skillet; cook 4 to 5 minutes on each side or to the desired degree of doneness. Remove steaks to a serving plate, and keep warm Repeat process with remaining 3 steaks. Top each steak with 1 to 2 tablespoons tarragon melting sauce. Serve immediately.
For tarragon melting sauce:
3) Position knife blade in food processor bowl; add all ingredients, and process until smooth. Cover, and refrigerate.
For the onion ring toppings:
4) Preheat oil to 180 degrees C/Gas 4.
5) Slice the onions into very thin rings and separate the rings. Spread them out and sprinkle with seasoned salt. Place the flour in a resealable plastic bag. Put the onion rings in batches, in the bag, close tightly and shake until the onion rings are coated.
6) Fry the onion rings in batches for 3 to 4 minutes, until they are brown and crispy.
7) Remove with tongs and drain on kitchen paper. Taste and season with salt, if necessary. Top the steak with the fried onion rings.