In a large mixing bowl, beat 1 cup of softened unsalted butter and ½ cup of granulated sugar together using an electric mixer on medium speed until light and fluffy, about 2-3 minutes.

Add the finely grated zest of 2 key limes, mixing for an additional 30 seconds.

In a separate bowl, whisk together 2 cups of all-purpose flour and ½ teaspoon of salt until combined.

Gradually add this mixture to the creamed butter and sugar, mixing until just combined.

Turn the dough out onto a clean surface and shape it into a log about 12 inches long and 1.5 inches in diameter.

Wrap the log tightly in plastic wrap and place it in the freezer for at least 30 minutes.

Preheat your oven to 375°F (190°C) and line two baking sheets with parchment paper.

Once the dough has chilled, slice it into ¼-inch thick pieces and arrange on the baking sheets.

Bake for approximately 12 minutes, rotating halfway through, until edges are golden.

Transfer the cookies to a wire rack to cool completely.

In a small bowl, whisk together 1 cup of powdered sugar and the juice of 1-2 key limes until smooth.

Once cookies are cooled, glaze the tops and allow to set for 15-20 minutes before serving.