Add the onions to the pot and sauté for 10 minutes, stirring frequently to prevent sticking. Part of the key to browning/caramelizing onions without oil is to only add them to a hot pan, then let them sit on the hot pan until they are browning without touching, then stir and periodically add only a tbsp or 2 of broth or water at a time to prevent burning and to deglaze. The onions brown at a higher temperature than water boils, so if the pan is constantly in too much moisture, then onions will have hard time getting to browning point. Only add enough periodically to prevent burning.