Preheat oven to 400 degrees with rack in center. Butter a 10-inch tart pan with a removable bottom; set aside.
In a medium bowl, whisk to combine flour, sugar, and salt.
In a small glass measuring cup, stir together butter, vanilla, and 1/2 tablespoon water; pour over flour mixture. Stir to combine.
With floured hands, press dough into prepared pan. Bake for 10 minutes. Remove tart shell from oven.