For the orange soufflé, cut the oranges in half and carefully hollow them out, squeezing out the juice while making sure that no white parts get inside.
Clean the orange halves and set aside. Boil down the orange juice in a saucepan without a lid with the sugar. Separate the eggs.
Beat the egg yolks with the sugar and vanilla sugar in a bowl until creamy and thick and light yellow. Preheat the oven to 200 degrees. Whip the egg whites until stiff peaks form.
Stir the amaretto and a few spoonfuls of orange juice into the egg yolk mixture. Gently fold in the snow. Place the orange halves on a deep baking tray and fill them with the mixture, leaving a finger-wide rim.
Brown the soufflés on the middle rack until they have risen and taken on some color or until the top is golden brown. (About 10 minutes).
In the meantime, make the sauce. Season to taste with amaretto and lemon juice, if desired. Now take out the finished soufflés, arrange them on a plate with the warm sauce and serve them on the spot, as the soufflés collapse very quickly.