Mix the rhubarb, sugar and vanilla sugar, cover and leave to infuse for approx. 10 mins.
Using the whisk on a hand mixer, beat the eggs, sugar and salt for approx. 5 mins. until the mixture is frothy. Mix in the almonds, flour and rhubarb, divide the mixture into the prepared ramekins.
Bake for approx. 25 mins. in the lower half of an oven preheated to 180°C. Remove from the oven, dust with icing sugar.