Preheat broiler to high; place a rack 5 inches from heat. Line a baking sheet with foil. Place bread slices on baking sheet and toast, turning once, until golden, 2 to 4 minutes. Rub one side of each slice with 1 clove garlic.
Sprinkle steak with salt and pepper, place on baking sheet and broil, turning once, 7 to 10 minutes for medium-rare. Tent with foil and let rest 5 minutes.
Put lettuce and tomatoes in a large bowl. Make dressing: Whisk together all ingredients. Pour on salad; toss to coat.
Arrange salad on 6 plates. Thinly slice steak and place on top of salad. Serve with toasted bread.