1. Make pastry. Combine flour and salt in a medium bowl. Gradually add the butter and shortening, tossing gently until all the pieces are coated with flour. With a fork, cut in butter and shortening until mixture resembles coarse crumbs. Add the lemon juice to 2 tablespoons ice water, then add to pastry, tossing vigorously until mixture just begins to hold together. (Add more water, a tablespoon at a time, if necessary.) On a smooth surface, shape pastry into 2 balls, one slightly larger than the other. Flatten into 2 thick disks. Wrap tightly in plastic wrap and refrigerate 1 hour or overnight.
2. Adjust oven rack to lowest position. Heat oven to 425 degree F.
3. Make filling. Combine sugar, flour, cinnamon, nutmeg, and salt in a large bowl. Add apples and lemon juice, toss well to coat. Set aside.
4. On a waxed paper-lined work surface, roll the larger pastry disk with a floured rolling pin into a 13-inch circle. Fit the pastry into a 9-inch deep-dish pie plate. Turn the apple mixture into the pie shell. Dot with butter. Trim the pastry leaving a 1-inch overhang. Roll the remaining pastry disk into an 11-inch circle. Cut out a small circle in the center with a small sharp knife. Lay pastry over apples. Trim edge, turn under and crimp. Place pie on a baking sheet, and bake 15 minutes. Reduce heat to 375 degree F and bake until apples are tender, about 45 to 50 minutes more. Makes 8 servings.