Heat a large grill pan over medium-high heat or prepare a medium-high (400°F) gas or charcoal grill fire.
In a baking dish just large enough to hold the steak, combine the Worcestershire sauce and 1 tsp. olive oil. Add the steak and turn to coat both sides.
Combine the vinegar, mustard, honey, garlic, 1/2 tsp. salt, and several grinds of black pepper in a small bowl. Slowly whisk in the 1/4 cup olive oil.
Brush the onion slices with the remaining 2 tsp. olive oil, and grill until tender, about 4 minutes per side. Season the steak with salt and pepper and grill alongside the onion, flipping once, 3 to 5 minutes total for medium rare. Transfer the steak to a cutting board, tent with foil, and let rest 5 minutes.
Toss the greens and tomatoes with just enough of the vinaigrette to coat lightly and divide among serving plates. Slice the steak across the grain, separate the onion into rings, and arrange both over the greens. Sprinkle the blue cheese over the salad, drizzle with additional dressing, if you like, and serve.
nutrition information (per serving):
32, Fat Calories
290, Saturated Fat
30, Monounsaturated Fat
9, Polyunsaturated Fat
Photo: Scott Phillips