Caramelized Onion & Gruyère Sandwich Recipe

It is always interesting to watch onions, full of tear-jerking sulfur in raw form, slowly caramelize and transform into silky strands that are sweet in both texture and flavor. As long as you have 40 minutes to prepare the onions (with only a few minutes of actual work), you will be left with a great filler for sandwiches, omelettes, soups, pizzas and pies. Here, a classic pairing with gruyère cheese, which can be substituted with swiss if necessary.