Heat the olive oil in a large, non-stick pan over medium high heat. Add the onions and salt and cook, stirring often, until the onions soften and start to brown.

Reduce heat to medium low and cook, stirring occasionally, until the onions collapse completely and turn to a rich, jammy brown, about 30 minutes.

When the onions are nearly done, add water and stir, scrapping the browned bits from the bottom of the pan into the onions. Set aside to cool. Makes 1 cup.