Wash fully ripened grapes. Separate the grape pulp and skins. In a sauce pan over medium heat cook grape pulp slowly until soft. Rub cooked pulp through a sieve. Combine the sieved pulp and grapes skins.
Mix the flour and sugar together and add to grape mixture. Stir in the melted butter and pour into one 9 inch unbaked pie shell. Cover top with strips of pastry. You can make a lattice pattern if desired.
Bake at 425 degrees F (220 degrees C) for about 25 minutes.