Red Wine Caramelized Onions

1) Thinly slice a red onion (slice it with – as opposed to against – the grain of the onion).
2) In a large sauté pan, add the butter and the olive oil and melt over medium heat.
3) Add the red onions and sprinkle with kosher salt.
4) Cook the onions until soft and the pan starts to dry out – about 5 minutes.
5) Add the wine to the pan, and scrape the browned bits up. Continue to cook on low heat another 15 minutes. Whenever the pan gets dry, add ¼ cup of water.
6) After the onions have been cooking about 20 minutes total, add the vinegar and sugar and cook another 5 minutes. The pan should be dry.
7) Scrape all of the onions into a bowl and refrigerate until ready to use.