Place piecrust in a 9-inch tart pan according to package directions. Bake at 400° for 9 to 11 minutes or until lightly browned.
Beat eggs and sugar in a large bowl until pale yellow. Stir in buttermilk and next 4 ingredients. Pour mixture into prepared crust. Sprinkle lightly with nutmeg. Bake at 325° for 12 to 15 minutes or until set. Cool before serving.