Preheat oven to 350 degrees.
Freeze the steak for 30 minutes. Slice very thin.
Season with salt, pepper, onion powder, and garlic powder. Toss to combine.
In a large skillet over medium high heat, add a little oil. Cook the steak for about 2 minutes, or until cooked through. Set aside.
Add the peppers and onions. Season with a little more salt.
Cut the rolls right down the middle, leaving them all in tact.
Spread mayo on the top and bottom. Place 6 slices of cheese on the bottom. Add the steak, then the peppers and onions. Place the remaining 6 slices of cheese on top. Place the tops of the rolls back on.
Brush the tops with butter. Sprinkle with a little salt and sesame seeds.
Bake for 10-15 minutes, or until toasted and the cheese is melted.
