1. Preheat oven to 400 F
2. Whip the egg yolks with one third of the granulated sugar until a pale yellow color. About 3-4 minutes on high speed of a mixer. Reserve and set aside in a new bowl so that you can use your mixer bowl for the egg whites. 
3. Add egg whites in clean, dry mixing bowl and whip on the lowest speed until slightly foamy. Then add in one third of the sugar and the lemon juice. Turn the mixer up to a medium speed until frothy (about 1 minute) and then turn to high speed to mix until about tripled in volume (2 more minutes). 
4. Then gradually add in cornstarch and last third of sugar. Keep whipping on high until stiff peaks form (roughly 3-4 minutes). 
5. To your mixing bowl, gently fold in your reserved egg yolks and sugar mixture, and slowly fold in your sifted flour. 

If piping, pipe onto a Silpat or parchment on a cookie sheet and pipe desired shape and size of cookie. Typically cookies are 2 inches long. Bake for 8-9 minutes until golden brown. Store in an airtight container. 

If making a single layer using cake pans or a 1/2 sheet tray, pour batter evenly between 2 cake rounds, or onto 1 1/2 sheet pan and try to even out the top. You can very gently shake the pans to try to get the batter to settle, but don’t shake too much or you’ll ruin the air bubbles. Bake for 10-12 minutes, turning the pan halfway through. The top should be golden and the edges will pull away slightly. You can also stick a toothpick in the center, and once it comes out clean, remove from oven. 

Let cool completely before cutting or shaping.