Sieve the starch and icing sugar into a bowl. Beat the egg white until very stiff. Then gradually add the starch mixture and ##vinegar## and continue beating until the beaten egg whites are shiny white. Line a baking tray with baking paper. Draw a circle (approx. 24 cm Ø) on it. Pour the beaten egg whites into the circle and form a "cake" with the help of a tablespoon the size of the circle.
Press a depression in the middle. Bake in a preheated oven (electric cooker: 125 °C/ convection oven: 100 °C/ gas: not suitable) for approx. 4 hours, then reduce the temperature if necessary (electric cooker: 80 °C/ convection oven: 60 °C). Let the meringue cool down in the oven when it is switched off. ##Clean, wash and cut the rhubarb into pieces of approx. 2 cm length, put them into a pot, sprinkle with 50 g sugar and let them steep for approx. 30 minutes. Bring 180 ml juice and lemon juice to the boil, add rhubarb and steam covered for about 3 minutes. Remove the rhubarb. Mix pudding powder and 2 tbsp. juice. Bring the juice to the boil again and thicken with the pudding powder. Fold in rhubarb. Pour the compote into a bowl and let it cool down. Mix vanilla sugar and 3 tbsp. sugar.
Bring the juice to the boil again and thicken with the pudding powder. Fold in rhubarb. Pour the compote into a bowl and let it cool down. Mix vanilla sugar and 3 tbsp. sugar. Remove meringue from baking paper and place on a suitable plate. Whip the cream until stiff and allow the sugar mixture to trickle in. First pour ##cream##, then rhubarb compote onto the meringue and serve immediately
waiting time approx. 2 hours