I'm a huge fan of making actual meals out of left overs instead of just heating them back up. The caramelized onions and sauce are easy to make and transform the cold boring leftovers into something even better than the original meal. I suppose one could add melted cheese to this but I don't think it's necessary.
beef
sweet onion
bread
mayo
fresh lemon juice
garlic
fresh thyme
To caramelize onions a little bit faster than normal start the onions in a dry pan and wait to add the butter when they are hot and starting to glisten (about 5 min). I can't remember why this makes them go faster but a chef told me about it once and I remember it making sense. Plus, it works.
For the sauce I start with the minced garlic and some salt and then add the mayo and lemon juice. Always use fresh lemon juice, store bought stuff will ruin any sauce. I threw in some thyme because it seems to go well with beef and was in the fridge but you could experiment with other herbs too.
