Bacon, Egg, & Cheese Quiche

1, 9 inch unbaked pie shell, chilled
2 tablespoons butter
1 large onion, sliced
1 pound bacon, sliced
4 eggs
2 cups light cream
3/4 teaspoon salt
1/8 teaspoon nutmeg
1/8 teaspoon cayenne pepper
1/8 teaspoon pepper, ground
1 cup Swiss cheese, grated