PREPARE and bake single pie crust according to recipe directions, using a 9-inch pie plate; cool.
MELT butter in medium saucepan. Add rhubarb and 1 C. sugar. Cook, stirring occasionally, over low heat until rhubarb is tender.
COMBINE remaining 1/4 C. sugar, 3 Tbsp. corn starch and salt in small bowl. Stir in egg yolks and heavy cream. Add to rhubarb mixture. Cook and stir until thick. Cool to room temperature. Refrigerate until cold. Spoon into cooled baked pie crust.
COMBINE cream cheese and powdered sugar in small bowl. Beat at medium speed of electric mixer until blended. Beat in whipped topping. Spread evenly over rhubarb.
COMBINE strawberries, 1/4 C. powdered sugar and 4 1/2 tsp. corn starch in small saucepan. Cook, stirring constantly, until thick. Cool to room temperature. Refrigerate until cold. Spread evenly over cream cheese layer.
HEAT oven to 350ºF.
BEAT egg whites and cream of tartar at high speed of electric mixer until soft peaks form. Beat in 1/2 C. granulated sugar, 1 Tbsp. at a time, until sugar is dissolved and stiff peaks form. Spread over strawberry filling, covering completely and sealing to edge of pie crust.
BAKE 10 minutes or until brown. Cool to room temperature before serving.
*Increase corn starch to 1/4 C. if using frozen rhubarb.