Preheat the oven to 350 degrees F. Make the crust and topping: Combine the flour, granulated sugar and salt in a medium bowl and mix with a fork. Drizzle in the melted butter and mix until well combined. Remove 3/4 cup of the mixture to a small bowl; add the hazelnuts and mix with your fingers until large clumps form. This will be the topping; refrigerate until ready to use. Press the remaining mixture into the bottom and up the side of a 9-inch pie plate. Freeze until firm, about 10 minutes.
Prick the bottom and side of the crust in several places with a fork. Line with foil, then fill with pie weights or dried beans. Bake until lightly golden around the edge, 12 to 15 minutes. Remove the foil and weights (if the foil sticks to the crust, you may need to bake it a few more minutes). Continue baking until the bottom of the crust is dry and lightly browned, 5 to 8 more minutes. Transfer to a rack and let cool 5 minutes, then use a small spoon to gently press together any small cracks while the crust is still warm. Spread the jelly over the bottom and up the side; let cool completely.
Meanwhile, make the filling: Whisk the pumpkin puree, half-and-half, granulated sugar, eggs and cinnamon in a large bowl until smooth. Set the cooled crust on a rimmed baking sheet; pour in the pumpkin filling (it will be quite full). Bake 20 minutes, then remove from the oven and sprinkle with the hazelnut topping. Continue baking until the filling is set, 30 to 40 more minutes. (Tent with foil if the pie is browning too quickly.) Transfer to the rack and let cool completely. Lightly dust with confectioners' sugar just before serving.