Clean, wash and slice the rhubarb. Sprinkle with 1 tablespoon of sugar and let it stand. Separate the eggs. Mix egg yolks, salt, vanilla sugar and 50 g sugar with the whisk of the hand mixer until creamy.
Stir in cream, orange liqueur and flour. Beat the egg whites until stiff, then add 50 g sugar. Fold the beaten egg whites into the dough in 2 portions. Spread half the rhubarb in a greased ovenproof dish (approx. 26 cm Ø) or pan (upper Ø approx. 30 cm) and pour the mixture on top.
Spread the rest of the rhubarb on top. Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for approx. 35 minutes. Dust the clafoutis with icing sugar. Serve with vanilla sauce.