Beat the yolks in a bowl on medium speed for about 2 minutes. Whisk together 1 cup of sugar, the flour and the salt. Slowly add the sugar and flour mixture to the yolks. Beat this mixture until it falls in ribbons from the beater blade. Scald the milk; add it very slowly beating all the time.
Pour yolk mixture into a saucepan. Add the butter or margarine to the saucepan. Cook while stirring, over medium heat, until the custard thickens; this will take 3 to 5 minutes. Do not let boil. Remove from heat, and add the vanilla and the raisins. Cover immediately with plastic wrap.
Beat the egg whites to stiff peaks. Beat in, slowly, 6 tablespoons sugar and cream of tartar. Make sure the filling is still hot, and pour filling into the crust. Top right away with the meringue; spread to the edges.
Bake at 325 degrees F (165 degrees C) for 20 to 25 minutes, or until browned. Cool pie on wire rack. Serve warm or at room temperature.
