Cut stem and root off onions and place stem side up in center of aluminum foil. Place one tablespoon of butter or margerine on top of each onion, then wrap up so that the foil has a point on top. Make sure it is wrapped good.
Place onions on a baking sheet and bake for 1-2 hours, depending on how soft you want them.
When finished, open up the top of the tin foil and pour the Italian dressing on top to taste. I like to use a lot.