Put the rice, milk, salt, vanilla sugar, lemon zest, butter and sugar in a saucepan. If you like it a little sweeter, add more sugar accordingly. Bring to a boil. Simmer over a low flame and the lid closed for about 20 minutes. Stir frequently so that nothing burns. Then take the pot off the stove and let it cool down with the lid closed.
Preheat the oven to 190 ° C.
Separate eggs. Beat the egg whites until stiff, stir in the egg yolks into the rice. Fold in the egg whites. Grease and flour a baking dish and pour in the rice mixture. Bake in the preheated oven for about 45 minutes. Sprinkle with powdered sugar.