Peel and halve pears, the core (preferably with a melon-ball cutter). Heat butter in a 9- to 10-inch well-seasoned cast-iron skillet over moderate heat until foam subsides, then stir in sugar (sugar will not be dissolved). Arrange pears, cut sides up, in skillet with wide parts at rim of skillet. Sprinkle pears with cinnamon and cook, undisturbed, until sugar turns a deep golden caramel. (This can take as little as 10 minutes or as much as 25, depending on pears, skillets, and stove.) Cool pears completely in skillet.
Put oven rack in middle position and preheat oven to 425°F.
Roll out dough on a lightly floured surface with a floured rolling pin into a 12-inch round and trim to a 9 1/2- to 10 1/2-inch round. Arrange pastry over caramelized pears, tucking edge around pears inside rim of skillet. Bake tart until pastry is golden brown, 30 to 35 minutes. Cook on rack 5 minutes.
Invert a rimmed serving plate (slightly larger than skillet) over skillet and, using pot holders to hold skillet and plate tightly together, invert tart onto plate. Serve tart warm or at room temperature.
Gourmet, November 2003; originally published November 1997, Adapted from Betty Caldwell