For the compote, clean and wash the rhubarb and cut the stems into small pieces. Caramelise 50 g sugar in a pot. Add half the rhubarb. Simmer for about 5 minutes. Add the rest of the rhubarb and simmer for about 1 minute more.
Pour into a bowl and leave to cool.
Place the lady fingers close together in an ovenproof dish (e.g. 18 x 24 x 5 cm) and sprinkle with the orange juice.
For the cream, mix mascarpone, quark, 125 g sugar and vanilla sugar. Spread the cream loosely on the lady fingers, spread the rhubarb compote in splodges and fold lightly into the quark cream.
Tiramisu should be covered and left to cool for about 2 hours. Roughly chop the pistachios. Sprinkle Tiramisu with them before serving.