Preheat the oven to 325°
Grate the zest from 2 lemons, and set aside. Then squeeze the juice out of all the lemons into a small bowl.
In large glass bowl mix the sugar and egg yolks with a electric mixer until the yolks are very thick and pale. Add the lemon juice and zest. Mix.
Move the bowl to a double broiler over barley boiling water and whisk constantly.
Whisk for 15-20 minutes, yes its a lot but think of it as a good arm workout. Its is worth the work, trust me!
After the time is up the mixture should be thick. Set aside.
Now beat the eggs whites until you get very stiff peaks
Fold into the lemon mix.
Now pour it all into the tart with graham crust. Carefully spread the filling evenly in the tart shell.
Bake for 15 minutes or until the filling is set.
Let the it cool. Then decorate.
I like to sift powdered sugar around the edge of the tart all the way around by the edge. Add some fresh berries and mint.
ENJOY!