Place bacon in a large skillet, and fry over medium-high heat until crisp. Drain on paper towels, then chop coarsely. Sprinkle bacon, cheese and onion into pastry shell.
In a medium bowl, whisk together eggs, cream, salt, sugar and cayenne pepper. Pour mixture into pastry shell.
Bake 15 minutes in the preheated oven. Reduce heat to 300 degrees F (150 degrees C), and bake an additional 30 minutes, or until a knife inserted 1 inch from edge comes out clean. Allow quiche to sit 10 minutes before cutting into wedges.