*  3 tablespoons olive oil
  * 1 large red onion, sliced
  * 3 tablespoons brown sugar
  * 1/4 cup red wine vinegar
  * 3 tablespoons water

 Heat the olive oil in a large skillet over medium-low heat. Add the onions and cook until soft and translucent about 10 to 15 minutes. Add the sugar, red wine vinegar and 3 tablespoons water and cook until the liquid is reduced completely and the onions are caramelized, about 10 minutes. 

BE CAREFUL as you approach carmelization - there's a very fine line between done and burnt.

tags: vegetarian, vegan, pareve

source: http://www.foodnetwork.com/recipes/brian-boitano/grilled-cheese-sandwich-with-red-onion-jam-recipe/index.html