Heat oven to 425 degrees. Prepare pastry. Mix peaches and lemon juice. Stir together sweetener, flour and cinnamon; mix with peaches. Turn into pastry-lined pie pan; dot with margarine. Cover with top crust which has slits cut in it; seal and flute.
Cover edge with 2-3" strip of aluminum foil to prevent excessive browning; remove foil last 15 minutes of baking.
Bake 35-45 minutes until crust is brown and juice begins to bubble through slits in crust.