In a medium bowl, whisk together the flour, cornstarch, and salt until combined. Set aside.

In a large bowl, beat the butter and ¾ cup granulated sugar together on medium-high speed until creamed, about 3 minutes.

Add the lemon zest, lemon juice, egg, and vanilla bean paste and beat on high speed until combined, about 1 minute.

Add the dry ingredients to the wet ingredients and mix on low speed until combined. Cover and refrigerate for at least 3 hours.

Line large baking sheets with parchment paper.

Scoop cold dough and roll into balls. Roll each ball in granulated sugar and place on lined baking sheets.

Use your thumb to make an indentation in the center of each cookie dough ball. Fill with lemon curd.

Preheat oven to 350°F (177°C). Bake shaped cookies for 12–13 minutes.

Allow cookies to cool on the baking sheet for 5 minutes, then transfer to a wire rack.

In a small bowl, whisk together confectioners’ sugar and lemon juice. Drizzle over cooled cookies.