Preheat oven to 375°F. Line a baking sheet with parchment paper or a silpat. Set aside.

In a medium bowl, whisk together flour, baking powder and salt. Set aside.

In a stand mixer, beat butter and sugar until light and fluffy. Add egg and lemon zest, mixing until combined. Add flour mixture 1/2 cup at a time, mixing until completely combined.

Roll one tablespoon of dough into small circles and then press with hands (or with the bottom of a cup) into a disk shape. Place on prepared baking sheet.

Bake for 8-10 minutes, until the centers are set. The cookies will not look browned or cooked, but they are. Remove from oven and let cookies rest on baking sheet for 5 minutes. Then transfer to a wire rack to cool completely.

Once ready to frost cookies, whisk together powdered sugar and lemon juice until smooth.

Using a spoon, smooth icing onto the top of each cookie. Top with fresh lemon zest, if desired. Let icing set for 10 minutes, or until hardened. Store in airtight container for up to 5 days.