Cut butter into pieces. Knead butter, flour, icing sugar, 1-2 pinches of salt and egg to a smooth dough. Wrap dough in foil and put it in a cool place for about 30 minutes. Wash and clean the rhubarb and cut it diagonally into pieces. Roll out the dough on a floured work surface until round (approx. cm 30 Ø) and line a greased tart tin (approx. 24 cm Ø) with it.
Press the edges firmly and cut off any excess dough. Prick the dough several times with a fork. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 15-20 minutes. Remove the tart and let it cool down. Stir 50 ml cherry juice and pudding powder until smooth. Bring 200 ml juice and 1 tablespoon sugar to the boil. Cook the rhubarb pieces for about 2 minutes, then thicken with the pudding powder. Simmer while stirring for about 1 minute. Fill the compote into the tart and chill for 1-2 hours. Shortly before serving, beat the egg whites until stiff, pour in 80 g sugar. Fill the beaten egg whites into a piping bag with star-shaped spout and sprinkle small tuffs onto the tart.
Bring 200 ml juice and 1 tablespoon sugar to the boil. Cook the rhubarb pieces for about 2 minutes, then thicken with the pudding powder. Simmer while stirring for about 1 minute. Fill the compote into the tart and chill for 1-2 hours. Shortly before serving, beat the egg whites until stiff, pour in 80 g sugar. Fill the beaten egg whites into a piping bag with star-shaped spout and sprinkle small tuffs onto the tart. Bake the tarte under the grill of the oven on the lower shelf for a few minutes until light brown. Serve the tarte immediately
45 minutes waiting time