Grease an ovenproof dish (approx. 26 cm Ø). Clean, wash and cut the rhubarb into pieces. Sprinkle with 1 tbsp. sugar and leave to stand for approx. 10 minutes.
Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer). Separate eggs. Beat the egg whites until stiff and allow 50 g sugar to trickle in. Chill the beaten egg whites. Whisk the egg yolks, 50 g sugar, vanilla sugar and 1 pinch of salt until creamy.
Alternately stir in cream, orange juice and flour. Fold in 2 portions of beaten egg white.
Put half the rhubarb in the mould. Pour egg mixture over it. Spread the remaining rhubarb on top. Bake in a hot oven for about 35 minutes. Cover with aluminium foil at the end of the baking time so that the surface does not become too brown.
Remove the clafoutis from the oven, dust with icing sugar and serve while still warm. Serve with vanilla cream sauce or ice cream.