For the caramelized onions
Place a saucepan over medium to high heat. Add olive oil and sauté the onion, stirring frequently. Season with salt and continue to sauté until the onion begins to brown and add sugar. Allow to caramelize, add vinegar and reduce heat. Cook until the vinegar has been completely absorbed and the onion is soft. If necessary, add a little water. Cool and store in the fridge.