On the stove top, cook bacon. Remove bacon and chop.
Drain off the bacon drippings reserving 2 tablespoons in the pan. Add the onions, brown sugar, garlic, salt and pepper to the pan and cook until the onions are golden brown and caramelized.
Add the bacon, caramelized onion mixture, cream cheese, sour cream, mozzarella cheese, and the diced tomatoes to a 4 quart slow cooker and stir to combine.
Cover and Cook on HIGH for 2 hours or until the cheese has melted stirring occasionally.
Serve on warm with tortilla chips or bread pieces.