Step 1

Whisk together flour, baking powder, baking soda, cornstarch, and salt in a medium bowl. Place sugar and Meyer lemon zest in a food processor and pulse for one minute. Beat butter and Meyer lemon-sugar in a large mixer bowl at medium speed until creamy; beat in egg, lemon juice, and vanilla until combined. Reduce speed to low and gradually add flour mixture; beat just until incorporated. Cover dough and chill in the refrigerator for 3 to 4 hours or overnight.

Step 2

Preheat oven to 350°F (if cookie dough has chilled overnight, let stand at room temperature for 30 minutes before baking). Line two baking sheets with parchment paper.

Step 3

Place granulated sugar and powdered sugar in separate shallow bowls. Use a cookie scoop coated with nonstick spray to scoop 1 1/2-inch balls of dough. Drop the balls of dough in granulated sugar and roll to coat, then coat generously in powdered sugar. Place two inches apart on prepared baking sheets.

Step 4

Bake, rotating pans halfway through, for 14 to 15 minutes, until edges are set and tops are matte (not shiny). Cool for 10 minutes on baking sheets, then transfer to a wire rack to cool completely. Store in an airtight container at room temperature.