Preheat oven to 350 degrees F (175 degrees C). Line a cookie sheet with parchment paper.

In a medium bowl, whisk together flour, baking powder, and salt.

In a large bowl, cream together sugar and butter until light and fluffy.

Add eggs one at a time, mixing well after each addition.

Stir in vanilla extract.

Gradually add the dry ingredients to the wet ingredients, mixing until just combined.

Scoop dough onto prepared baking sheet using an ice cream scoop.

Bake for 17-20 minutes, or until golden brown around the edges.

While cookies are hot, use your thumb to make a large indentation in the center of each cookie.

Cool completely on the baking sheet.

To make the lemon curd, whisk together lemon zest, lemon juice, sugar, and egg yolks in a medium saucepan.

Cook over medium-low heat, stirring constantly, until the curd thickens, about 5-7 minutes.

Remove from heat and stir in cold, cubed butter one piece at a time, until emulsified.

Pour curd into an airtight container and place plastic wrap directly on top to prevent skin from forming. Refrigerate.

To make the meringue, combine water, sugar, and corn syrup in a small saucepan over medium heat.

Stir until sugar is dissolved. Attach a candy thermometer and raise the heat to medium-high. Cook without stirring until it reaches 240 degrees F.

While the sugar mixture is heating, beat egg whites in a stand mixer until frothy.

Add cream of tartar and continue beating until stiff peaks form.

Slowly drizzle the hot sugar syrup into the egg whites while the mixer is on low speed.

Once all the syrup is incorporated, increase the mixer speed to medium-high and beat for about 7 minutes, until the bowl is cool and the meringue is thick and glossy.

Stir in vanilla extract.

To assemble the cookies, generously fill the indentation in each cookie with lemon curd.

Place several mounds of meringue on top and smooth with an offset spatula, covering the cookie entirely.

Turn on the broiler and broil until the meringue is golden brown.