Place raisins in bowl. Cover with boiling water; let stand 5 minutes to plump raisins. Drain.
Combine 1 cup sugar, flour and 1/8 teaspoon salt in 4-quart saucepan. Gradually stir in milk; cook over medium heat, stirring constantly, 7- 9 minutes or until bubbly and thickened. Remove from heat.
Place egg yolks in bowl; stir. Gradually stir 1 cup warm milk mixture into beaten yolks. Return egg mixture to saucepan, stirring constantly. Cook over medium heat, stirring constantly, 3-5 minutes or until mixture is thickened and coats back of metal spoon. Continue cooking, stirring constantly, 2 minutes. Remove from heat. Stir in drained raisins, sour cream and butter. (Do not over mix.)
Combine hot water and cornstarch in 1-quart saucepan; cook over medium heat, stirring constantly, 3-4 minutes or until mixture comes to a boil and is clear and thickened. Cover; refrigerate 8-10 minutes or until slightly cool.
Heat oven to 350°F.
Combine egg whites, cream of tartar and 1/8 teaspoon salt in bowl; beat at low speed until foamy. Beat at high speed, gradually adding 6 tablespoons sugar until glossy and soft peaks form. Add cornstarch mixture and vanilla to egg white mixture; beat until smooth.
Pour hot raisin filling into baked pie shell. Spread meringue over hot raisin filling, sealing to edges. Bake 10-12 minutes or until meringue is golden brown. Cool on cooling rack before serving. Cover; store refrigerated.