Special equipment: 9 by 2 1/2-inch deep foil pan
Whisk the eggs and cream together in a large mixing bowl. Add the salt, pepper and nutmeg and whisk to blend.
For the Lorraine tart: put the onion into a small skillet with a tablespoon of olive oil. Place the pan over medium heat and cook until the onion is translucent, about 10 to 15 minutes. Brush the bottom of the prepared tart shell with the Dijon and spread the cooked onion, bacon and Gruyere on top. Pour the custard over the filling and place the pan into the bottom half of the preheated oven. Bake the tart until the filling is slightly puffed and golden, about 40 minutes. Remove from the oven and let cool 10 minutes before serving.
For the olives, roasted red pepper and goat cheese tart: Put the olives, roasted red pepper and goat cheese into the prepared tart shell and pour the custard over the filling. Bake as above.
Prepare the tart pan by spraying it with pan release spray and coating it with the cornmeal. Knock out any excess cornmeal and set the pan aside.
Blend the flour and salt in the bowl of a food processor fitted with a steel blade. Add the butter and pulse until the mixture resembles coarse crumbs. Transfer the mix to a large mixing bowl and add the water 1 tablespoon at a time, stirring constantly with a fork. Transfer the dough to a floured surface and knead just until it forms a ball. Flatten the dough into a disk and wrap in plastic wrap. Refrigerate at least one hour.
On a floured surface, roll the dough out to a 12-inch circle. Carefully lift it into the prepared pan, pressing into the bottom and up the sides. Leave at least a 1-inch overhang, which will be used to crimp the edges. Prick the bottom of the pan all over and place in the freezer for 15 minutes.