Prepare:
Position a rack in the lower third of the oven. Preheat the oven to 425°F.
Roll the dough into an 11- to 12-inch round. Transfer the dough to a baking sheet. Brush the pastry with a thin coat of:
Reserve the rest of the butter. Sprinkle the pastry with:
Peel, core, and slice ⅛ inch thick:
Leaving a 1-inch border all around the edge, arrange the apple slices in slightly overlapping concentric rings on the pastry. Fold the border of dough over the edges of the apples. Brush or drizzle all but about 2 teaspoons of the remaining melted butter over the apples. Combine in a small bowl:
Sprinkle the cinnamon sugar over the apples. Bake until the pastry begins to brown, 15 to 20 minutes. Reduce the oven temperature to 350°F and bake until the pastry is golden brown, 5 to 10 minutes more. Brush the apples with the reserved butter. Serve warm or at room temperature.