Line a 9-inch pie plate with half of pastry. Combine sugar, flour, rind, cinnamon, and salt; stir well. Sprinkle one-third of mixture into pastry shell. Top with apple slices. Sprinkle remaining sugar mixture over apples; dot with butter.
Cover with top crust, and slit in several places to allow steam to escape; seal and flute edges. Brush pastry lightly with beaten egg white. Bake at 450° for 10 minutes; reduce heat to 375°, and bake an additional 30 minutes.