Roll out the dough 1/8 inch thick on a lightly floured surface, fit it into a 10-inch (6-cup capacity) pie plate, and flute the edge decoratively. Chill the shell while making the topping and the filling.

Make the topping:

In a small bowl blend together the butter, the sugar, the cinnamon, and the flour until the mixture is combined well and chill the topping, covered, while making the filling.

Make the filling:

In a large bowl whisk together the sour cream, the sugar, the salt, the vanilla, the eggs, and the flour until the mixture is smooth, add the apples, peeled, cored, and sliced thin, and stir the filling until it is combined well.

Spoon the filling into the chilled shell, smoothing the top, and crumble the topping evenly over it. Bake the pie in the middle of a preheated 350F. oven for 1 to 1 1/4 hours, or until it is golden and the apples are tender, transfer it to a rack, and let it cool completely.