Simmer milk with lemon zest for 10 mins then let it cool down.
Whip egg whites and set aside.
Mix egg yolks with sugar and vanilla, add flour and cornstarch, your milk and finally your whipped egg whites.
Pour everything into a baking dish covered with parchment paper and bake for 50 mins (170C).
Let your cake cool down completely then rest in the fridge for at least 2-3 hours (better overnight).
