Apricots andchopped pistachios top a layerofrich pistachio cream on a rectangle of puff pastry.
Process 1 cup nuts and the granulated sugar in a food processor to combine. Add butter; process until a paste forms. Add egg, vanilla, and salt; process to combine. Set aside.
On a lightly floured surface, press edges of both pastry sheets together to form one large sheet. Roll out to a 9-by-17-inch rectangle; transfer to a baking sheet. Spread reserved pistachio mixture over dough, leaving a 3/4-inch border.
Position rectangle so that a short end is nearest you. Arrange apricots on top in 4 vertical rows, alternating direction in which apricots face from row to row. Fold in edges of dough; use your index finger to make a scalloped border. Refrigerate until cold, about 30 minutes.
Preheat oven to 400 degrees. Whisk together yolk and cream; brush egg wash over edges of tart shell. Chop remaining tablespoon nuts; sprinkle nuts and turbinado sugar over apricots. Bake, rotating sheet halfway through, until crust is deep golden brown and fruit is juicy, about 35 minutes. Let cool on a wire rack.
Meanwhile, heat jam with 1 1/2 tablespoons water in a small saucepan over low heat, stirring, until thinned, about 2 minutes. Pass through a fine sieve into a small bowl. Brush glaze over fruit.