Add the vinegar/wine, water, and sugar and stir until the sugar melts. Increase the heat to medium-high and bring to a boil. Lower the heat and simmer until thick, about 10 minutes, stirring occasionally. You want them to become almost creamy.
Serve over steak, on in mixed with vegetables, on toast (Italian toast: crostini or bruschetta), crackers, appetizers like cream chilled filled celery sticks or sliced cucumbers, and so much more. You may also package and freeze for future use.
https://glutenfreerecipebox.com/caramelized-red-onions-with-balsamic-vinegar-red-wine/