• Prepare several cookies sheets by lining them with parchment paper.

Cookie Dough

• Place butter, sugar, and salt in the mixing bowl of an electric mixer. Beat until smooth and creamy, about 2 minutes.
• Add the egg yolk, lemon juice, vanilla extract, lemon zest, and fresh thyme and beat until the mixture is well mixed.
• Gradually add flour to butter-lemon mixture, beating until the dough just comes together, about 1 minute. It will be sticky. Place dough between 2 pieces of parchment paper and press or roll into a rectangle that is approximately ¼" thick. Place on cookie sheet and refrigerate for 4 hours to overnight.
• Preheat the oven to 300°F.
• Remove the dough from the refrigerator and cut the cookies out with a 3-inch scalloped or round cookie cutter. Place them on parchment-lined cookie sheets, allowing about 1-½" of space in between. Prick each cookie in the center with the tines of a fork.
• Bake the cookies for 20-22 minutes or until they are just starting to turn golden on the bottom.
• Cool the cookies on the cookie sheet on a wire rack for 5 minutes then remove to the wire rack to cool completely.

Lemon Glaze

• While the cookies are cooling, make the glaze.
• In a medium bowl, whisk together the lemon juice and powdered sugar until smooth. Start with 2 tablespoons lemon juice and slowly add more until you reach a spreadable or drizzle consistency. Brush the glaze over the cooled cookies then decorate immediately by sprinkling tops with lemon zest and thyme. Let the glaze set before storing, about 30 minutes.