Clean, wash and drain the rhubarb and cut it diagonally into slices. Separate 5 eggs and chill egg white in a fat-free bowl. Dice marzipan. Beat the fat, bourbon vanilla sugar, marzipan, salt and 200 g sugar until creamy with the whisk of the hand mixer.
Add 3 eggs and egg yolks one after the other and stir in. Mix flour and baking powder and stir in alternately with the sour cream. Put the dough on a well greased baking tray, smooth it down and spread rhubarb evenly on top.
Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for approx. 25 minutes. About 5 minutes before the end of the baking time, beat the egg white and lemon juice until stiff. Sprinkle 250 g sugar into the mixture.
Pour into a piping bag with a large star-shaped spout. Take the cake out of the oven and place it on a grid. Spray 5 strips spirally from the long side onto the cake (at a distance of approx. 2.5 cm).
Bake the cake at the same temperature for another 18-20 minutes. Remove from the oven and allow to cool on a cake rack. Dust meringue strips with icing sugar.