Preheat oven to 450 degrees. Place pie crust in a pie plate and trim the edges. Flute or decorate the edge of the dough as you like.
In a medium bowl beat the eggs and stir in the cream, onion, salt and cayenne pepper. Set aside.
In another small bowl, gently mix the crabmeat and the cheese together. Sprinkle the crab and cheese mixture over the bottom of the pastry in the pie plate, covering the bottom evenly. Pour the egg mixture over the crab mixture evenly, and do not stir. Sprinkle with parsley (optional).
Bake the pie for 15 minutes. Reduce the heat to 300 degrees and bake for another 25-30 minutes, until a cake tester or a knife inserted an inch deep into the center of the pie comes out clean.
Let quiche rest for 15 minutes before cutting into wedges.