Place potatoes in a medium saucepan and cover with lightly salted water. Bring to a boil; simmer for 15 to 20 minutes or until tender. Drain and quarter potatoes; place in a large bowl. Stir in celery, red onion and scallions.
In a small bowl, whisk together oil, vinegar, sugar salt and pepper. Gently fold into potato mixture and cover with plastic wrap.
Heat broiler. Rub beau monde seasoning on both sides of steak. Broil for 3 minutes per side or until internal temperature reaches 135°. Allow to rest 5 minutes before thinly slicing against the grain.
Serve sliced steak with warm potato salad.
Make your own seasoning mixture: Combine 1 tbsp each celery salt, black pepper and onion powder.