1) Bake the uncut puff pastry shell in a 450 degree F oven for 4 to 5 minutes. Remove from oven. Reduce oven temperature to 375 degrees F.
2) Meanwhile, in a medium skillet, cook turkey and onion in butter over medium-high heat until onion is tender, but not brown. Sprinkle cheese over the bottom of the precooked shell. Pour the turkey mixture over the cheese.
3) In a medium bowl, whisk together the eggs, cream, mustard, salt, and red pepper. Pour over turkey-cheese mixture.
4) Bake at 375 degrees F for about 30 minutes. If necessary, cover the edge of the crust with aluminum foil to prevent over-browning. Let the quiche cool for 10 minutes before serving.