Cook bacon, drain on paper towels. When it's cool; dice.
Saute' onions in a large skillet with 1 tablespoon vegetable oil (or 1 tablespoon grease from bacon) on medium heat until tender and golden brown. This will take about 10 minutes. Stir regularly.
Using an electric mixer, mix cream cheese, mayonnaise, parmesan, hot sauce, and garlic powder until smooth. Add cheddar cheese and onion and mix until well incorporated.
Pour into a shallow 1 and 1/2 quart baking dish and bake at 350 degrees for 20 to 25 minutes or until hot throughout. Remove from oven and sprinkle bacon on top.
Serve warm or room temperature with crackers, tortilla chips or celery sticks.