In a small bowl, mix together the water, apple cider vinegar, and ice cubes. In a large bowl, whisk together flour, salt, and sugar. Add chilled butter cubes and cut into the dry mixture using a pastry cutter until the butter is in pea-sized and slightly smaller pieces. Add 2 tablespoons of the ice water-apple cider vinegar mixture, and continue to blend using pastry cutter until dough begins to come together. Use hands to knead dough gently into a uniform ball. If it’s too sticky, add a sprinkle or two of flour, until pliable but smooth. Shape dough into a disk and flatten into a 1-inch thick circle. Wrap in plastic and chill in refrigerator at least one hour.

Preheat the oven to 400ºLine a baking sheet with parchment paper.

In a small bowl, whisk together the ricotta, honey, and salt. In a medium bowl, toss the grapes with the cornstarch, sugar, and vanilla.

Roll out the pie crust into a 13" circle and transfer to the baking sheet. Spread the ricotta mixture over the crust, leaving a 2 ½" border. Arrange the grapes on top. Fold over the sides of the crust. In a small bowl, whisk the egg and water. Brush the crust with the egg wash. Bake for 30 to 40 minutes, or until golden brown.