1.Bring A Large Pot Of Lightly Salted Water To A Boil. Add Rotini Pasta And Cook For 8 To 10 Minutes Or Until Al Dente; Drain. 2.Heat Oil In A Large Saucepan Or Skillet, Add Onion, Bacon, Salt And Pepper. Cook Until Bacon Is Crispy And Onion Soft. Pour In Tomato Soup And Stir; Bring To Boil. Stir In Cheddar Cheese Until Melted And Thick. 3.Combine Sauce With Pasta In A Baking Dish, Trickle Milk Down The Sides Of The Dish And Stir Slightly. Sprinkle With Remaining Cheese. Place Under The Oven Broiler Until Sauce Is Thick And Cheese Browned.