The ultimate crowd pleasing party dip! This Cheesy Baked Onion Dip is made with sweet onion and a combination of cheddar and mozzarella cheeses. It's rich, creamy, cheesy and melts in your mouth. It is always hit when I serve at parties or bring to any type of gathering. Whether it be a picnic, game night, family gathering, Memorial Day, July 4th, Christmas, or any holiday entertaining. Everyone will beg you for this recipe! Ideally, you should use Vidalia onions but they don't come into…