Rub all sides of the steak with taco seasoning. Set aside and heat grill or grill pan to medium heat.
Add the steak to grill or grill pan and cook each side about 4 minutes or until done to preference.
Remove from heat and set on a cutting board to rest 2-4 minutes.
Meanwhile, wash and tear lettuce and divide over four plates. Add chopped cilantro, diced tomatoes and avocado slices. Slice the steak on a cutting board, against the grain.
Layer the steak over the lettuce, add the cilantro, tomato and avocado. Shred reduced-fat cheddar cheese over top and add salsa, if desired, for dressing.