Preheat your oven to 350°F (175°C). Line a baking sheet with parchment paper or a silicone baking mat to ensure your cookies don’t stick and bake evenly.
In a large mixing bowl, beat the softened unsalted butter and powdered sugar together using a hand or stand mixer on medium speed. Beat until the mixture is light, fluffy, and pale in color — about 3 to 4 minutes.
Mix in the vanilla extract and rose water until fully combined.
In a separate bowl, whisk together the all-purpose flour, finely ground pistachios, salt, and baking powder.
Gradually add the dry ingredients to the wet mixture. Mix just until the dough comes together, avoiding overmixing.
Using a spoon or cookie scoop, portion out dough into 1-inch rounds and place them about 2 inches apart on the prepared baking sheet. Gently press the tops of each cookie and sprinkle with the chopped pistachios, pressing lightly to adhere.
Bake for 15-18 minutes, or until the edges are just beginning to turn golden. The centers may still look soft; they will firm up as they cool.
Allow the cookies to cool on the baking sheet for about 5 minutes before transferring them to a wire rack to cool completely. Once cooled, dust generously with powdered sugar.