Preheat the oven to 425°F (218°C).
If the dough is very cold, let it warm on the counter until it feels pliable. Roll the dough out on a lightly floured work surface into a circle 6 to 7 inches (15 to 18 cm) in diameter.
Gently place the dough in the tart pan, pressing it firmly around the edges and trimming any dough that hangs over the edge. Prick the dough with the tines of a fork. Line the dough with parchment paper or aluminum foil buttered on its underside and fill the pan with dried beans, rice, or pie weights.
Bake for 10 minutes. Reduce the oven temperature to 375°F (190°C), remove the parchment or foil and weights, and prick the bottom again. Bake, uncovered, for 2 minutes more.
While the pastry is baking, crack the egg into a measuring cup and add enough cream to make a scant 1/2 cup. Add the salt and nutmeg and mix well.
Scatter the prosciutto, ham, or bacon over the crust and pour in the egg and cream mixture, which should fill the tart shell right up to the top. (If you have a little too much filling, save it to add to scrambled eggs the next morning.)
Carefully place the tart pan on a rimmed baking sheet lined with parchment paper or aluminum foil and bake until the quiche filling seems set in the center, about 25 minutes.
Remove from the oven and let the quiche rest until set, about 5 minutes. (Yes, you can wait that long before you dive in.) Set the table, shut down the computer, have a seat, and help yourself.