sauté onions in a little PAM until they get nice and brown
cook the cauliflower until it is VERY soft ( I steam the florets so they are more nutritious)
mash the cauliflower, add the sautéed onions, season with salt and pepper if you wish
hint: To caramelize onions, cook them very slowly until they get nice and brown. (I start with a spritz of PAM but keep adding a little veggie broth or water to keep them going).