The best rhubarb cake is crispy on the outside and juicy on the inside, sweet and sour in a match made in heaven.
Rhubarb is a special plant, originally coming from China. In the early Middle Ages it reached Europe through Arabic medicine. The name is therefore, based on medieval Latin roughly translated as “foreign root”. However, it is not so much the roots that are suitable for eating, but rather the long and juicy stems. Rhubarb cannot be eaten raw because the plant contains oxalic acid – you should be careful eating this in large quantities. However, in the right dosage rhubarb is healthy, refreshing and very tasty.
Rhubarb is a basis for many delicious foods, including juice or syrup, jam, compote or – as today – cake.
We love the slightly sweet and sour flavor, most red rhubarb varieties also have a delicate raspberry taste to them. This recipe is definitely the best rhubarb cake we know of (at this point, a very special thanks to our friend Caro for the fantastic recipe), because it combines a crispy edge with an incredibly juicy-sweet filling.
Let’s get to work on the dough first. This is a slightly more refined shortbread dough, which also contains an egg compared to the basic version. The special thing about shortcrust pastry is that the delicately crispy dough keeps its shape well during baking, i.e. it does not expand much, because no leavening agent such as yeast or baking powder is used. The rule of thumb for shortcrust pastry is 1-2-3 – (1 part sugar, 2 parts butter, 3 parts flour), very easy to remember. It works perfectly for quiche and tartes of all kinds. Feel free to be creative!
We need a large mixing bowl, in which we can work well by hand. In this bowl we combine all the ingredients.
Now people with cool hands have an advantage. The less the butter softens, the better the shortbread will be. If the butter is too warm or if the dough is kneaded for too long, the ingredients separate – the dough becomes strangely crumbly, the professionals call it “brandy” dough. The trick is to use your fingertips to crumble the ingredients until the dough can be pressed together into a homogeneous ball.
Of course, you can also use the dough hook of a mixer. But even then you should be careful not to overwork the dough. Stop as soon as everything is mixed well.
You can flatten the resulting ball a bit and then wrap it in foil or put it in a tight box and chill it in the fridge for at least 30 minutes.
Now it’s time for the filling. You can get the best rhubarb at farmers markets or straight from the garden, like we did. But at the right time of year, rhubarb is also available at the supermarket.
Wash the rhubarb briefly and remove any remaining soil. With a small, sharp knife you can cut a little at the end and pull off the top layer. The rhubarb doesn’t have a true “skin” – but the outermost layer is usually a bit firmer than the inside, and we don’t want that in a delicious cake. Depending on how firm your rhubarb is, you can peel thinner or thicker. For fresh rhubarb, just peel off a millimeter.
We now cut the rhubarb into cubes. Do not cut too small – during baking the rhubarb almost dissolves. However, the texture of the pieces is very tasty in the cake, after all, we do not want to have a uniform mush as a filling.
Now we whip the egg whites and cream with a mixer (whisk). First for the egg white. To make the egg whites easy to whip, it’s important to use a clean container and clean whisks, and to make sure there are no egg yolk residues in the liquid. However, we don’t need egg whites that are firm to the touch here, just a frothy, airy mixture – you don’t have to beat for too long.
Then we whip the cream separately and add the sugar and vanilla sugar at the end. Whipping is best done in a narrow, tall container and with the cream as cool as possible.
In a large mixing bowl, we now carefully fold the whipped cream into the rhubarb pieces with a spatula. Then we sift the flour into it, continuing to mix the filling with the spatula. Finally, fold in the egg whites. The right order should help to keep as much air as possible in the filling. Now you can chill the filling until the dough is ready.
The dough should be cool enough to handle. If the dough is still too sticky to roll without problems, you need to chill it a little longer.
Now you can preheat the oven to 200 degrees – if you use convection, 165 degrees will do.
First cut off about one third of the dough for the edge and roll it into a long strip. Roll out two thirds of the dough as a round plate for the base. By the way, you may roll out the dough not only with a rolling pin, but also with a wine bottle (washed clean, of course). The cool bottle prevents the dough even better from sticking to the rolling pin.
In a 28 cm springform pan you now shape the dough with your fingertips.
We are not very perfectionist about this task here. French patissiers creating the finest pastries have completely different standards. For our cake, it is sufficient to create a thin and reasonably even crust.
We prick the bottom with a fork a few times before the first baking, so that it doesn’t form any bumps while baking. If you’re feeling fussy, you can also place a piece of baking paper cut to the size of the dough base with some added weight on top of the dough, such as dry beans, peas or chickpeas, the process called “blind baking.” In this way, the dough becomes especially smooth and even.
We pre-bake the dough for 10 minutes before filling. Take care to distribute the mixture well, so that the rhubarb pieces are spread evenly.
The cake will now bake for about 50 minutes. Put it in the oven at medium height so that it browns evenly all over. You can check if it is done by poking a wooden stick (e.g. a chopstick) in the middle and no liquid is visible when you take it out.
To ensure that the cake separates well from the edge of the form, you can carefully help along the edge with a sharp knife before opening the springform pan.
The finished rhubarb cake. You can dust it with a little powdered sugar if you like. Serve well chilled with whipped cream.
And may the taste be with you.
250 g flour
125 g butter
65 g sugar
1 packet vanilla sugar
1 kg rhubarb
180 gr sugar
¼ l cream
70 gr flour
1 packet vanilla sugar
2 egg whites
Springform pan 28 cm
Pre-bake the dough for 10 min
Baking time 50 min at 200 degrees (with convection oven 165 degrees)