How to Make It
In a medium bowl,gently toss the raspberries with 2 tablespoons of the sugar and the zest and juice from the lemon.Refrigerate for 30 minutes.
Meanwhile,line a rimmed baking sheet with parchment paper.Unfold the pastry on a flat surface,roll it to a 12-by-15-inch rectangle and cut into three even 12-by-5-inch rectangles.Transfer to the prepared baking sheet and freeze for 20 to 25 minutes.
Preheat the oven to 425 degrees F.Dust the puff pastry with 2 tablespoons of the sugar.Cover the pastry with a wire baking rack to prevent puffing as the pastry cooks.Bake until golden brown,about 22 to 25 minutes.Remove the rack and let cool.
In the bowl of a stand mixer fitted with the whisk,beat the heavy cream,vanilla bean seeds and the remaining 1 tablespoon of sugar until soft peaks form,3 to 5 minutes.
Place a spoonful of the whipped cream in the center of a rectangular platter and top with one sheet of puff pastry.Spoon over half of the whipped cream in the center leaving about 1 inch clear around the edges.Arrange about 1/3 of the fresh raspberries on top of the cream in rows.Top with another sheet of pastry and repeat with the remaining cream and another 1/3 of the raspberries.Add the last piece of pastry glaze-side up.Top with the remaining raspberries and serve immediately.