Spread apples evenly in bottom of pie shell.In separate bowl, cream sugar and butter.Blend in lemon juice and 3 beaten egg yolks.Pour over apple.Sprinkle with cinnamon and nutmeg.Bake in 350 degree oven for 40 to 45 minutes. Beat egg whites until peaks are formed.Gradually, add powdered sugar and vanilla, beating until meringue is stiff.Spread over top of pie.Return to oven.Reduce heat to 325 degrees.Bake 5 to 10 minutes longer, until meringue is lightly browned.