Preparation

• Whisk the flour, cornstarch, baking soda, and salt together in a medium bowl. Set aside.
• In a large bowl, beat the butter and granulated sugar together on medium-high speed until creamed, about 3 minutes. Add the egg, lemon juice, lemon zest, and vanilla extract and beat on high speed until combined, about 1 minute. Mixture will appear curdled. Scrape down the sides and bottom of the bowl. Add the flour mixture and beat on low speed until combined. Dough is thick, creamy, and sticky.
• Cover dough tightly and chill in the refrigerator for at least 3 hours and up to 3 days.
• Remove cookie dough from the refrigerator. Let it sit at room temperature for about 10 minutes if chilled longer than 3 hours.
• Preheat oven to 350°F (177°C). Line baking sheets with parchment paper.
• Scoop and roll balls of dough, about 1 Tablespoon each, into balls. Roll in granulated sugar first, then in confectioners’ sugar. Place 3 inches apart on the baking sheets.
• Bake the cookies for 12–13 minutes or until edges appear set and centers look soft.
• Cool cookies for 5 minutes on the baking sheet, then transfer to a cooling rack to cool completely.
• Cookies stay fresh covered at room temperature for up to 1 week.