Source: Rebar by Audrey Alsterberg and Wanda Urbanowicz
Heat oil and butter in a skillet until butter starts to foam. Add onions and salt and cook for 20 minutes. Stir in sugar and wine (if using) and cook until liquid is evaporated. Add stock or water, vinegar pepper and herbs and cook until liquid evaporates again.
Serve caramelized onions on pizza, sandwiches, to add flavour in soups or sauces or stirred into sour cream to use as a dip.