Cook sugar in small saucepan over medium heat until it dissolves and turns golden brown. Remove from heat and stir in butter and vanilla bean seeds.
Preheat oven to 180°C/360°F. Peel, core, and cut apple into medium-thick slices. Arrange in concentric circles over caramel.
Cut out a circle of puff pastry large enough to cover apples. Score circle all over with the tip of a sharp knife. Place pastry over apples, pressing it down gently to cover.