Combine flour, confectioners' sugar, and salt in a bowl. Add cubed butter and rub everything together until mixture resembles fine bread crumbs. Add egg yolk and combine until a solid ball of dough is formed. Work in pistachios and rose petals.

Roll dough into a log, approximately 1 inch in diameter and 10 inches long. Wrap in plastic wrap and chill in the fridge for 2 hours, or up to 5 days if making ahead.

Preheat the oven to 325 degrees F (165 degrees C). Line a baking sheet with parchment paper.

Remove plastic wrap from dough once it's chilled and solid. Unwrap and slice into 1/4-inch rounds and place on the prepared baking sheet.

Bake in the preheated oven until shortbread has a light golden color, about 15 minutes. Cool and store in an airtight container.