In a large bowl, beat eggs. Add sour cream. Stir in sugar, 2 tablespoons flour, vanilla and salt; mix well. Gently stir in apples. Pour into pie shell. Bake at 375° for 15 minutes.
Meanwhile, combine brown sugar and remaining flour; cut in butter until mixture is crumbly. Sprinkle over top of pie. Bake 20 to 25 minutes longer or until filling is set. Cool completely on a wire rack. Serve or cover and refrigerate. Yield: 8 servings.