Melt a bit of butter in a pan and saute the onions. Sprinkle a little salt and pepper.
Slice a wedge in your roll so you're able to add more filling without breaking the bread into halves.
Season the beef with salt and pepper and place in the pan to brown. Once browned check seasoning and add the cheese on top. Fold the meat over and add more cheese.
Place in your roll and be sure to include that lovely dripping grease.