1) Put all marinade ingredients in medium bowl and whisk to combine.
2) Put the steaks and half the marinade in a food-safe plastic bag and turn steaks to coat them well. Close bag securely and marinate in refrigerator for at least 15 minutes to 2 hours. Cover the remaining marinade and chill, it will be used for dressing.
For the steak:
1) Preheat barbecue or griddle, medium heat.
2) Remove steaks from refrigerator and discard marinade. Place steaks in center of griddle, sprinkle with pepper and arrange onion slices around the sides.
3) Griddle steaks, uncovered, 15 to 18 minutes for medium-rare to medium doneness, turning occasionally.
4) Griddle onions 15 to 20 minutes or until tender, turning occasionally.
5) Carve steaks into slices, cut onion slices into quarters, then toss cabbage, onion and 2 tbsps of the reserved dressing in large bowl.
6) Arrange beef slices on the cabbage mixture and drizzle with some of the dressing. Put remaining dressing in a small jug to hand around the table .