1 . Stage
Mix sugar, flour and salt, mix with a fork to break the lumps and set aside.
2 . Stage
Beat egg yolks, butter and lemon zest. Continue to beat, add lemon juice. Then, alternating, gradually add the flour mixture and milk, stirring until smooth.
3 . Stage
Beat egg whites in a separate bowl. Carefully add them to the dough.
4 . Stage
Put the dough in a baking dish and put them on a steam bath. Put in the oven and bake for 45 minutes at 180 degrees. Cool slightly, sprinkle with powdered sugar.