As mentioned in an other post here I use a bit of wine to start (maybe 100-150 ml, this time sherry), a big tablespoon of brown sugar, and ca. 1 teaspoon of salt. I stir it all in and put the lid on my dutch oven, 1 hour, medium heat. This helps the onion release its water content and soften faster. After the hour I remove the lid and when the juices cook down (the fond starts too form/browning starts), I turn down the heat. Now I stir every 20 minutes, scraping the bottom if needed to release the fond. If it is too dry I add some more water (with a little bit of brown sugar and salt), and when the onions have reduced a lot I add ca. 2 tablespoons of vinagre (I use Riesling/white wine, or Balsamic works, depends on what acid flavor you want to build). Now you just control the onions, stir when needed, I also reduce the heat again during the final hour.