Cut the rhubarb into slices of approx. ½ cm. Mix the rhubarb slices with 1 tablespoon of sugar and let them sit for 5 minutes while you prepare the cake batter.
Turn on the oven and preheat it to 180 degrees Celcius ordinary heat.
Find a springform pan of approx. 22 cm in diameter. It should be thoroughly greased with butter and then sprinkled with flour.
Melt the butter in a saucepan and set it aside to cool slightly.
Beat eggs and sugar together until fluffy and white, use a mixer. Then add the vanilla paste and beat for a little more time.
Flour and baking powder are now added to the mixture of eggs and sugar. Whisk it slowly until it becomes a smooth dough. Then add the butter gradually until the dough is evenly mixed. Finally, add 2/3 of the rhubarb and turn the dough around a few times so that they are evenly distributed.
Pour the dough into the greased springform pan. Spread the last 1/3 of the rhubarb over the cake and press them down lightly. Also feel free to pour the juice from the rhubarb over the top of the cake.
Now the cake must be baked at 180 degrees Celcius for approx. 40 minutes, or until you can stick in the cake with a needle without the raw dough sticking to it.
When the cake is done, take it out of the oven to cool.
Now the cake is ready to serve. You may want to give the cake a sprinkle of pearl sugar or icing sugar on top.
Serve the cake as it is or with whipped cream, vanilla ice cream, or sour cream.