Preheat the oven to 350°. Line a baking sheet with parchment paper or a silpat. Place the pie pastry into a pie plate and press the crust firmly to the bottom and sides of the dish. Fold the overhanging parts under and use the tines of a fork or your fingers to create a decorative border. Place the pie plate on the baking sheet and set aside.
Heat the olive oil over medium high heat in a skillet. Add the onions and saute until tender, about 5 minutes. Set aside.
Place the crab in a large mixing bowl. Pick through the meat with your fingers removing any cartilage or shells you might find. Add the sautéed onions and parsley.
In a small bowl, whisk the eggs with the half and half. Add the salt, pepper and cayenne, stirring to combine. Pour the egg mixture over the crab and stir. Add 1 cup of the gruyere cheese and stir until just combined. Transfer the crab mixture to the pie shell. Scatter the remaining gruyere cheese and parmesan on top of the quiche. Place the quiche in the oven and bake for 50 minutes to an hour until the center of the quiche is set. Remove from the oven and let it rest for 20 minutes before cutting.
Can be made a day ahead and reheated in a 300° oven for 15-20 minutes.