Make the dough: In a bowl, cream butter and powdered sugar together until smooth and fluffy. Add lemon zest, lemon juice, and vanilla. Mix until combined.
Add dry ingredients: Stir in flour, ground pistachios, and salt. Mix just until a soft dough forms. Do not overmix.
Chill: Shape dough into a log or disk, wrap in plastic, and refrigerate for 30–60 minutes until firm.
Bake: Preheat oven to 165 °C (325 °F). Roll or slice dough into 1 cm thick rounds. Place on parchment-lined baking sheet. Bake for 12–15 minutes, until edges are just starting to turn golden.
Cool & dust: Let cookies cool slightly, then dust generously with powdered sugar while still warm for that perfect "snow" effect.
