Preheat The Oven'S Broiler And Set The Oven Rack About 6 Inches From The Heat Source. Stir Together The Luncheon Meat, Cheddar Cheese, And Salad Dressing In A Bowl. Spread The Filling Onto The Cut Side Of Each Hamburger Bun, And Place Onto A Baking Sheet, Filling-Side Up. Broil The Open-Faced Sandwiches In The Preheated Oven Until The Tops Are Browned And Bubbly, About 5 Minutes.