In a food processor place flour, pistachios, powdered sugar and salt. Pulse a few times until well blended.
Add the butter 1 cube at a time and pulse to combine, then add the rosewater, vanilla and water. Blend until the mixture begins to form a ball. Tip: Taste the dough for the level of rosewater flavor you want at this step. Add more as needed to taste.
Remove from food processor and place on a lightly floured surface. Bring together into a large ball.
Cut ball into two equal parts.
Roll out each part into a 9" log. Wrap with plastic wrap and place in the refrigerator for about 3 hours.
Preheat oven to 325°F.
Cut cookies into ½ inch circles and bake approximately 12-15 minutes or until they appear golden brown on the edge.
Sprinkle with powdered sugar after cool.