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.