You'll find yourself making this classic sandwich all year round. It's quick and easy for weeknights, but also great for weekend plans with friends.
Light a grill or preheat broiler.
To make marinade, combine shallot, vinegar and extra-virgin olive oil in a bowl. Season to taste with salt and pepper. Add rosemary. Spoon 2-3 tablespoons of marinade over steak and let stand at room temperature, covered, for 20-30 minutes. Reserve remaining marinade. Grill or broil steak to desired doneness. Let steak stand for 5 minutes, then slice thinly across the grain.
Meanwhile, brush both sides of bread with olive oil. Grill bread on lightly oiled grill rack, turning once, until golden, about 2-3 minutes. Rub each slice with garlic clove.
Place the lettuce, and tomatoes in a bowl and toss with reserved marinade. Divide steak into 4 servings and arrange on the grilled bread. Top each half with salad greens and another slice of bread. Serve immediately.