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

In a large bowl using a handheld or a stand mixer fitted with a paddle attachment, beat the butter and 3/4 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. Dough will be very creamy. Cover and refrigerate for at least 3 hours, and up to 3 days.

Line large baking sheets with parchment paper or silicone baking mats. Make room in the refrigerator for baking sheets.

Place granulated sugar in a small bowl. Scoop cold dough (about 1 Tablespoon of dough each) and roll into balls. Roll each dough ball in granulated sugar and place 2 inches apart on lined baking sheets.

Use your thumb to make an indentation in the center of each cookie dough ball. Fill each with 1/2 teaspoon of lemon curd.

Preheat oven to 350°F (177°C). Place baking sheets with unbaked cookies in the refrigerator while the oven preheats.

Once oven preheats, bake shaped cookies for 12–13 minutes, or until edges appear set and are very lightly beginning to brown. Remove from the oven and allow cookies to cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.

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