Preheat oven to 200F. Grease pan with butter and coat with flour. Beat egg whites with electric beater until foamy. Gradually add in sugar until batter is stiff and silky. Put batter into pastry bag and squeeze onto pan. Bake for 3 hours or until meringues are dry and can be easily removed from pan. Put a wooden spoon handle in the door to keep from closing all the way. Allow to cool completely before storing in an airtight container at room temperature.