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

In a large bowl, cream together the unsalted butter and granulated sugar until light and fluffy, about 3-5 minutes. Beat in the egg, followed by the fresh lime juice and lime zest.

In a separate bowl, whisk together the all-purpose flour, baking powder, and salt. Gradually add this dry mixture to the wet ingredients, mixing until just combined.

Cover the bowl with plastic wrap and refrigerate the dough for about 30 minutes.

Scoop portions of the chilled dough onto the prepared baking sheet and bake for 10-12 minutes until the edges are lightly golden.

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

For the optional glaze, mix the powdered sugar with lime juice and drizzle over the cooled cookies.