Fit the puff pastry (you can also use a regular pie crust if you prefer) to a 9 inch tart pan. Pierce the bottom with the tines of a fork about 15 times. Place the pan in the freezer and chill for at least 20 minutes.
After chilling, prebake the crust in the oven for 12 minutes at 400°F. Remove from oven and allow to cool for at least ten minutes before filling.
Meanwhile, melt the butter in a medium sized skillet on low-medium heat. Add the shallots and cook for five minutes, stirring frequently to avoid browning. Add the salmon and heat just until the salmon is cooked through.
Remove from heat and spread the filling in the cooled crust.
Sprinkle evenly with shredded cheese.
Whisk the eggs, creme fraiche, salt, pepper, and cayenne together until combined. Pour on top of the other ingredients and place the quiche in the oven to bake for 40 minutes at 375° F.