Preheat oven to 350 degrees.
Fill the pie shell with apple slices. Scatter dots of butter over apples.
Sprinkle with cinnamon. Bake until apples are cooked.
Beat egg whites with cream of tartar until medium stiff.
Continue beating and gradually add the sugar. Beat until firm.
Cover pie with meringue. Bake until meringue is golden brown.
Cool. Serve at room temperature.
I like it with cinnamon ice cream.