Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.

In a medium bowl, whisk together the flour, baking soda, and salt until well combined.

In a large mixing bowl, cream together the room-temperature butter and granulated sugar until light and fluffy, approximately 2-3 minutes.

Beat in the egg, followed by the key lime juice and lime zest until everything is well incorporated.

Gradually add the flour mixture to the wet ingredients, stirring until just combined; be careful not to overmix.

Using a tablespoon, drop rounded mounds of dough onto the prepared baking sheet, leaving space between each cookie to allow for spreading.

Bake in the preheated oven for 10-12 minutes, or until the edges are lightly golden, keeping an eye on them to prevent over-baking.

Let the cookies cool on the baking sheet for about 5 minutes before transferring them to a wire rack to cool completely.

For the glaze, mix the powdered sugar with the tablespoon of key lime juice until smooth, then drizzle over the cooled cookies.

Finish with a sprinkle of lime zest for garnish.