Preheat oven to 375°. In a small bowl, mix flour and salt; cut in shortening until crumbly. Add egg, stirring with a fork. Press mixture onto bottom and up sides of a greased 11x7-in. baking dish. Bake until lightly browned, 20-22 minutes. Cool on a wire rack. Reduce oven setting to 350°., In a small bowl, beat egg whites with vanilla and cream of tartar on medium speed until soft peaks form. Gradually add 3/4 cup sugar, 1 tablespoon at a time, beating on high after each addition until sugar is dissolved. Continue beating until stiff glossy peaks form. Fold in almonds., Drain cherries, reserving juice. Add enough water to juice to measure 1 cup; pour into a saucepan. Stir in tapioca, egg yolks and remaining sugar; let stand 5 minutes. Bring to a boil over medium heat, stirring constantly; cook and stir until thickened, about 2 minutes. Stir in cherries, lemon juice and, if desired, food coloring., Pour into crust. Immediately spread meringue over top, sealing edges to crust. Bake until meringue is golden brown, 22-25 minutes., Cool 1 hour on a wire rack. Refrigerate at least 3 hours before serving.