Beat the egg whites with the cream of tartar and the salt and pepper to taste. Evenly divide the egg whites and place each portion on a piece of toast. Make a hole in the middle and carefully drop an egg yolk in the hole and cover it up with the egg white. Carefully add 2 slices of bacon to the top of each egg nest and bake at 350 degrees for 20 min. Add the grated cheese to each one and bake a few more minutes until the cheese is melted. The bacon will finish cooking in the oven and the toast will become toasted.