For the compote clean, wash and cut rhubarb into pieces. Mix 5 tablespoons cherry juice and starch until smooth. Bring the rest of the juice, 50 g sugar and vanilla sugar to the boil in a pot, cover and simmer for about 5 minutes until the rhubarb falls apart.
Stir the mixed starch into the boiling compote, bring to the boil and simmer while stirring for about 1 minute. Remove from the heat and allow to cool slightly. Sweeten if necessary.
Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer). Dice bread very finely. Wash lemon hot and dry. Finely grate the peel. Bring milk, lemon zest, 2 tablespoons of sugar and 1 tablespoon of butter to the boil in a saucepan.
Stir in the bread cubes and let it stand for about 15 minutes.
Grease four ovenproof moulds (each containing approx. 200 ml) or one large mould (approx. 800 ml). Separate 2 eggs, chill the egg white. Stir egg yolk and 1 egg into the bread-milk mixture. Spread the mixture evenly into the moulds.
Bake in a hot oven for 20-25 minutes.
Beat the egg whites until stiff and add 50 g sugar. Remove the ramekins from the oven. Spread 1 tbsp. rhubarb compote and beaten egg white on each. Bake in the oven at the same temperature for 12-15 minutes.
Take it out of the oven. Arrange dusted with icing sugar, add the rest of the compote.