While pasta cooks, brown beef and yellow onion in a large skillet over medium heat until no longer pink. Drain and return to skillet.
Season with steak seasoning, salt, and pepper.
Add ketchup, mustard, relish and diced tomatoes. Stir well to combine.
Cook 1-2 minutes for flavors to develop. Reduce heat to low.
When pasta is cooked, drain well. Add to skillet. Stir well to combine.
Sprinkle with cheese. Cover and keep on warm until cheese melts.
Sprinkle with green onions and serve.