Pulse flour and salt in a food processor until combined. Add butter, and process until mixture resembles coarse meal, about 10 seconds. With machine running, add ice water in a slow, steady stream until dough just comes together (no longer than 30 seconds).
If making tomato hand pies, divide dough in half, shape each into a square, and wrap in plastic. If making herb-leek tart, flatten dough into an oblong disk, and wrap in plastic. Refrigerate dough for at least 1 hour (or up to 2 days), or freeze for up to 1 month.