2Sift or whisk flour, salt, and baking powder together in a bowl.
3Place butter in a large mixing bowl and mix with a wooden spoon until very creamy. Add confectioners' sugar, lemon juice, and flour mixture; mix until well combined.
4Roll dough out on a lightly floured surface to 1/4-inch thickness. Cut into rounds using a round cookie cutter. Transfer cookies to ungreased baking sheets.
5Bake in the preheated oven until cookies are light brown on the bottom but still very light on top, about 10 minutes. Allow cookies to cool on the baking sheets for about 2 minutes before transferring to wire racks to cool completely.
6To make the glaze: Whisk melted butter and lemon juice together in a small bowl. Add lemon zest and whisk again. Whisk in confectioners' sugar 1 cup at a time. Add more lemon juice if necessary for a thin consistency.
7Dip the top of each cookie in the glaze and transfer to a wire rack placed over waxed paper or parchment paper. Allow cookies to sit until glaze has set, about 2 hours.
8Store cookies in an airtight container between layers of waxed paper.
Notes
Cookies will stay fresh for up to 1 week in an airtight container.