Spread 1 tbsp. dressing on both sides of bread. On parchment-lined baking sheet, bake bread at 400 degrees , 6 minutes. Turn, sprinkle with 2 tbsp. Parmesan and bake another 6 minutes. Form beef into 4 patties; season. In cast-iron skillet, cook patties over high, flipping once, about 4 minutes per side for medium-rare; transfer to bread. In bowl, toss romaine with remaining dressing and cheese; pile onto burgers.