In the work bowl of a food processor, pulse together nuts until finely ground. Add flour, salt, and sugar, and pulse until combined. Add cold butter, pulsing until mixture is crumbly, about 30 seconds. With processor running, add buttermilk in a slow, steady stream until a dough forms. Turn out dough, and shape into a disk. Wrap tightly in plastic wrap, and refrigerate for at least 30 minutes.
Recipe by Southern Cast Iron at https://southerncastiron.com/mixed-caramel-nut-tart/