Season each tuna steak with 1 teaspoon of the rub.
Sear the steaks in a nonstick skillet over high heat, 1 1/2 to 2 minutes on each side, less if you prefer it on the rare side. Remove and let cool for about 5 minutes. Flake the tuna with a fork.
Divide the salad greens and onions among 6 salad plates. Divide the tuna evenly into 6 portions and place on the greens. Garnish with tomato wedges. Top each with 1 tablespoon of the dressing.
Yield: 6 servings