In a large bowl mix together flour, salt, and cinnamon. Add apples and lemon juice. Toss until apples are thoroughly coated. Allow to sit for 10 minutes.
Pour apples into pastry-lined pie plate. Dot with butter or margarine. Cover with top pastry. Seal edges and cut steam vents in top pastry.
Bake in preheated oven for 35 to 45 minutes, until crust is golden brown.
