Sour Cream Apple Pie

Roll out dough on a lightly floured surface with a lightly floured rolling pin into a 13-inch round (1/8 inch thick), then fit into a 9-inch metal pie plate. Trim edge, leaving a 1/2-inch overhang, then fold overhang under and crimp edge decoratively. Chill shell 30 minutes. While shell chills, put oven rack in middle position and preheat oven to 400 °F. Whisk together eggs, sour cream, vanilla, 1 cup sugar, 3 tablespoons flour, nutmeg, and salt in a bowl until smooth. Peel and core apples, then cut into wedges slightly less than 1/4 inch thick. Arrange apples in pie shell, then pour sour cream mixture evenly over them, coating all apples. Bake pie 15 minutes, then reduce oven temperature to 350 °F and bake until filling is puffed and golden and apples are tender, 45 to 50 minutes. While pie bakes, stir together remaining 1/3 cup sugar, remaining 1/3 cup flour, cinnamon, and a pinch of salt in a bowl, then blend in butter with your fingertips until mixture forms small clumps. Remove pie from oven and increase oven temperature to 400 °F. Crumble topping evenly over top and bake until sugar is melted, about 10 minutes. Cool pie on a rack at least 45 minutes. Serve warm or at room temperature.