In a medium-sized mixing bowl whisk together flour, baking soda, and kosher salt, and set aside.
In the bowl of an electric mixer add granulated sugar, unsalted butter, lime zest, and vanilla extract. Mix until fluffy, about 5 minutes. Make sure to scrape down the sides of the bowl a few times while mixing.
Add in the fresh lime juice and large egg. Mix until combined.
Slowly add in the flour mixture and mix just until combined.
Let the dough rest for an hour in the fridge.
Shortly before baking preheat the oven to 350 degrees F and prepare baking sheets with non-stick spray or line with parchment paper.
Scoop out 2 tablespoon balls of dough and place on your prepared baking sheets. Leave 2 inches between cookies.
Place into the oven for 6 minutes, remove, flatten cookies to 1/4 inch thick with the bottom of a glass, and add back to the oven to bake for another 6 minutes.
Whisk together powdered sugar and lime zest and glaze the tops of the cookies.
If the glaze is too thick add more lime juice. If the glaze is too thin add more powdered sugar.
Top with chopped pistachios if desired.