I made this last night and it was sooo goood...
Left over steaks-sliced thin
1 red onion-sliced
1 green pepper- sliced
1 cup shredded cheddar cheese
I sauteed the onion and pepper in butter, then added the pre-cooked steaks, heated them through, then I topped it off with the cheese and just let it melt. I couldn't stop from eating it...add salt, garlic and pepper if you wish.
You could also do this with other leftovers like chicken, pork tenderloin...