Combine the flour, corn starch, salt, and baking powder in a large bowl, whisk together then set aside.
Add the room temperature butter, lemon zest and sugar to the bowl of a stand mixer fitted with a paddle attachment or a large bowl if using an electric hand mixer. Beat on a medium speed for about 3 minutes or until light and fluffy.
Add the egg yolks and vanilla extract then mix until combined. Scrape the bowl down and mix once more.
Dump in the dry mixture and mix on low until just combined. Scrape the bowl down one last time and mix for a few seconds more.
Transfer the dough onto a piece or plastic wrap and flatten into one or two disks. Wrap well and chill for about an hour.
Once you dough has chilled set oven to 350F and bring the dough out onto your counter to warm up for a few minutes. Roll out to between 1/4 and 1/8 an inch on a lightly floured surface. Use a circle or scalloped cookie cutter to cut the dough and transfer to parchment or silicone-lined baking sheets. Re-roll any excess dough and cut or freeze for later.
Bake for about 8 minutes rotating pan halfway through. Allow to cool on baking sheet before assembling.
Once cool you can pipe or smear a dollop of dulce de leche onto the back of a cookie and sandwich to the bottom of another cookie. Roll in shredded coconut and repeat assembly for the remaining cookies.