A golden puff-pastry shell is filled with vanilla-flecked mascarpone cream and topped with rows and rows of juicy raspberries in this impressive dessert.
Preheat oven to 400 degrees. On a sugared work surface, roll out pastry to a 16 1/2-by-12 1/2-inch rectangle, about 1/8 inch thick. Using a pizza wheel or a sharp knife, cut 1 1/4-inch strips from each side of dough. Brush a 1-inch border of egg wash around perimeter of dough and top with strips, overlapping corners and trimming ends to fit. Lightly press strips to adhere. Transfer to a parchment-lined unrimmed baking sheet and freeze until firm, about 15 minutes.
Using a paring knife, score strips with a pattern of diagonal lines. Using a docking tool or the tines of a fork, prick holes all over center of dough, creating steam vents. Score bottom crust along interior edges of strips. Freeze until firm, about 15 minutes.
Invert a wire rack over tart shell and transfer to oven. Bake until puffy and beginning to brown, about 20 minutes. Remove rack and continue baking until deeply golden brown, 15 to 20 minutes more. Transfer to a wire rack and let cool completely.
In the bowl of a mixer fitted with the whisk attachment, beat together mascarpone, vanilla seeds, lemon zest, and 1/3 cup sugar on medium speed until combined and slightly thickened, about 2 minutes. Add cream and continue beating until stiff peaks form. Spread filling evenly into tart shell. Top with raspberries and refrigerate at least 30 minutes before serving.