In a small bowl, combine all of the ingredients for balsamic dressing. Cover and set aside.
(I made my balsamic dressing ahead of time to let the flavors marinate together.)
Put together your salad in large serving bowl or plate. Add lettuce, top with halved cherry tomatoes and sliced onion.
Cook steak on grill to desired doneness. When steak is done, take off grill and let sit on a plate for a few minutes.
Place steak on top of lettuce, followed by blue cheese crumbles.
Drizzle your balsamic dressing on top, evenly.
Enjoy!