Combine water, raisins, vanilla pudding mix, sugar, and salt in a saucepan.

Cook and stir until the mixture comes to a boil and thickens.

Remove from heat and stir in butter, lemon juice, and lemon zest.

Cool for 5 minutes, stirring twice.

Pour the filling into the baked pastry shell.

Press a piece of waxed paper on top of the filling.

Refrigerate overnight.

Remove waxed paper.

In a bowl, combine sour cream, confectioners' sugar, and nutmeg.

Spread the sour cream mixture over the pie.

Store in the refrigerator until ready to serve.