Spread butter on bread slices and place 3 slices on the bottom of the baking dish. Cover with 1/2 of the cheese, and then repeat layer. In a small bowl beat together eggs, milk and salt and pour over bread layers. Refrigerate, and allow to stand until the liquid has been absorbed, several hours or overnight.
Preheat oven to 375 degrees F (190 degrees C). Lightly grease a 9x13 inch baking dish.
Cover and bake in preheated oven for 10 minutes. Remove cover and continue baking for 35 minutes more, or until brown and fluffy.