Line a 9-inch pie plate with a double layer of foil. Do not trim. Grease foil with butter on the bottom and up the sides to the top of plate. Arrange pecans or walnuts around side and on bottom of foil lined pie plate. Sprinkle with brown sugar.
In a large bowl combine the sugar, flour, cinnamon, salt and lemon juice. Add apples and toss to coat. Spoon over pecans. Place pastry over filling. Fold edge under and flute, cut slits in top. Turn foil up around edge.
Bake at 350 degrees for 45-55 minutes or until apples are tender. Invert onto a serving plate. Carefully remove foil. Serve warm.