Pre-heat oven to 350 degrees Beat egg whites with electric mixes (power 8 or high) until begins to be frothy. Slowly add cream of tartar. While beating, slowly add sugar. Beat until stiff peaks form. Add meringue to hot pie filling. First, spoon around edges of the pie, pushing meringue into crevices and being sure to seal against the crust. Then, add remaining meringue to the center of the pie. Mound high and create peaks with the back of a spoon. Put pies in oven, reduce heat to 325 degrees. Bake for 10 minutes. Turn oven off, leave pies in the oven for 10 more minutes to set and brown. Remove from oven; Put on rack to cool.