Hazelnuts give this dough a nice texture and a nutty flavor. You'll have one portion of dough left over after making the cauliflower tart; it's great for apple or pumpkin pie (just shape it into a disk instead of a rectangle).
Pulse flour, hazelnuts, and 1/4 teaspoon salt in a food processor until combined. Add butter, and pulse until mixture resembles coarse meal, about 10 seconds. Drizzle 1/4 cup ice water evenly over mixture, and pulse until it just begins to hold together (dough should not be wet or sticky). If dough is too dry, add more water, 1 tablespoon at a time, and pulse.
Divide dough in half, and shape each half into a rectangle. Wrap in plastic wrap. Refrigerate until firm, about 1 hour. Let stand for 10 minutes before rolling.
Make ahead: Dough can be refrigerated overnight or frozen for up to 3 months. Let chilled dough stand at room temperature for 10 minutes and frozen dough thaw before using.