Preheat oven to 400 degrees F (200 degrees C). Press pie crust into a 9-inch pie dish.
Arrange pear slices in the pie crust. Stir sour cream, 1/2 cup sugar, 2 tablespoons flour, egg, vanilla extract, and salt together in a bowl; pour over pears.
Mix 1/2 cup flour, butter, 1/4 cup sugar, and cinnamon together in a bowl until topping resembles coarse crumbs.
Bake pie in the preheated oven for 35 minutes. Sprinkle topping onto pie and continue baking until topping is golden brown, about 10 more minutes.
