Mix the butter, sugar and vanilla sugar until creamy. Separate eggs. Chill the egg whites. Stir the egg yolks one at a time into the butter mixture. Mix flour with baking powder. Mix in alternately with the almonds.

Grease a small baking pan (approx. 20 x 30 cm). Pour in the dough and press down a little on the bottom. Bake in the oven at 180 degrees for about 15 minutes.

Clean the rhubarb, cut into pieces approx. 3 cm long. Briefly bring to the boil with sugar and 4 tablespoons of water. Drain and drain.

Remove the base from the oven. Spread the rhubarb on top.

Beat egg whites with lemon juice until stiff. Sprinkle in the sugar. Beat until the mixture shines.

Pour egg whites into a piping bag and sprinkle dots on the rhubarb. Bake in the oven at the same temperature for about 15 to 20 minutes. Remove from oven and allow to cool.