Pulse nuts, sugar, and salt in a food processor until nuts are finely ground. Pulse in flour. Add butter, and pulse until dough resembles coarse meal, about 10 seconds. Add egg yolk; process until mixture just comes together, about 30 seconds.
Turn dough out onto a lightly floured work surface; pat into a disk. Press dough evenly into a 4-by-13 1/2-inch rectangular tart pan with a removable bottom. Chill until firm, at least 30 minutes.
Preheat oven to 375 degrees. Bake crust, pressing down halfway through, until edges start to feel firm, about 25 minutes. Transfer to a wire rack; let cool completely.