Heat oven to 275 degrees. Grease 9"x13"x2" glass baking dish. Beat egg whites, cream of tartar and salt until frothy; gradually add 1 1/2 cups sugar, about a tablespoon at a time. Continue beating until stiff and glossy, at least 5 minutes. Spread mixture in pan. Bake for 1 1/2 hours. Turn off oven. Leave meringue in oven with door closed for another hour.
Mix softened cream cheese, 1/2 cup sugar and vanilla. Fold in whipped cream and marshmallows. Spread over meringue and chill overnight.
Stir lemon juice into cherry pie filling and add strawberries and spread over cheese filling 1 hour before serving.
