Begin by placing softened unsalted butter and granulated sugar in a large mixing bowl. Using an electric mixer, beat on medium speed until light and fluffy, about 2-3 minutes.

Next, add the vibrant key lime zest to the butter-sugar mixture. Mix on low speed for approximately 30 seconds, just until the zest is evenly distributed.

In a separate bowl, whisk together all-purpose flour and salt until well combined. Slowly add this dry mixture to the butter mixture, using a spatula to gently fold them together.

Turn the dough onto a clean surface and shape it into a 12-inch log. Wrap the log in plastic wrap and place it in the freezer for about 30 minutes.

While the dough chills, preheat your oven to 375°F (190°C). Line your baking sheets with parchment paper.

After the dough has firmed, remove it from the freezer and unwrap it. Slice the log into ¼-inch thick discs. Arrange the slices on prepared baking sheets.

Bake in the preheated oven for about 12 minutes, until the edges turn a light golden brown.

Once baked, transfer the cookies to a wire rack to cool completely. Prepare the glaze by whisking together sifted powdered sugar and key lime juice until smooth.

Drizzle the glaze over your cooled cookies and allow it to set for 15-20 minutes before serving.