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.
