Preheat oven to 425°.
Cut 1 nectarine in half. Quarter one nectarine half and the remaining 6 nectarines.
Combine sugar, water, and juice in a 12-inch stainless-steel skillet. Cook for 2 minutes or until sugar is golden (do not stir). Remove from heat; stir in butter and vanilla. Let stand 3 minutes.
Place nectarine half, cut side down, in center of sugar mixture; arrange nectarine quarters, cut side down, around center. Return pan to medium heat. Cook for 10 minutes or until sugar mixture is bubbly (do not stir). Remove from heat; let stand 3 minutes.
Roll pie dough into a 12-inch circle on a lightly floured surface. Place dough over nectarine mixture, fitting dough between nectarines and skillet.
Bake at 425° for 15 minutes or until lightly browned. Remove from oven, and cool for 10 minutes. Carefully invert tart onto a serving plate. Cut into wedges.