“Zwiebelkuchen” is an ab-so-lu-te delicacy and yet only widespread in a limited region. In Germany – but not everywhere – onion tart is usually made with yeast dough and sometimes with shortcrust pastry, mainly with the year’s grape must or young wine and therefore seasonal. Less traditional but also delicious are versions with curd-oil dough. In Switzerland, there are “Zwiebelwähe” for the Basel carnival, Bern’s “Zibelemärit” and much more. In Alsace, they bake “Tarte à l’oignon”.
But that seems to be it, we are not aware of any similar preparations from other parts of the world – we would be delighted to hear of any evidence to the contrary.
Here we present a version from the south-west of Germany, for a whole, deep baking tray. With this quantity, many people will enjoy the dish and the recipe is perfect for a large group, a party or simply for more than one day.
We bake with yeast dough and as this needs to prove for a while, we start with it. Flour, sugar, salt, milk, optionally a little soft butter and yeast are mixed together and worked into a homogeneous dough. As always, the exact quantities can be found at the end of the recipe. This is done quickly in a kitchen machine, while by hand it takes a good 10 minutes. The finished dough is covered and then left to rest in a warm place for at least 30 minutes, 45 minutes is better. We always put the bowl of dough in the oven with only the light on.
Surprisingly, you now need a lot of onions. And traditionally, smoked bacon is also included, so this is not a vegetarian dish. The bacon can of course be omitted, but it makes quite a difference to the flavour.
The onions are peeled, halved and cut into thin strips, not too fine, but thin. Cut the bacon into thin strips or small cubes but remove any rind. If you like your onion tart a little firmer, you can also dice the onions, but we prefer the texture that comes from onion strips.
In a large pan, the onions are sautéed slowly in a little neutral oil (alternatively butter) over a medium-high heat (caution: never over a high heat), turning them repeatedly. They must not take on any colour. After 5 minutes, we add a little icing sugar to the onions to slightly enhance their natural sweetness. Nevertheless, this will be a savoury dish.
After 10 minutes, we add the diced bacon and continue to stir well so that everything is heated evenly.
After 15 minutes, we sprinkle a little flour over the mixture and stir again thoroughly. After a total of 20 minutes, the onions have broken down a little, are intensely fragrant and the fat in the bacon has turned translucent. Now we leave everything to cool.
In a large bowl, equal parts sour cream and cream, eggs, salt, grated nutmeg and ground caraway are mixed together. Yes, caraway. It has to be caraway, otherwise it’s not the same dish. For us, a surprising number of people don’t like the flavour of caraway and we do not use this spice on a daily basis either, but this is a dish that cries out for it. It’s exactly the flavour of caraway that brings everything together in the end. Try it for yourself and you’ll be convinced.
The slightly cooled onion mixture is added and everything is thoroughly mixed together, then it is time to continue with the dough.
We grease a deep baking tray at least 2.5 cm high with butter.
The dough is rolled out on a lightly floured work surface so that it overlaps the baking tray by about 4 cm. Then we place the dough on the baking tray and gently press it into its shape. Just below the edge of the baking tray, we trim off the excess dough all round with a sharp knife, pour in our filling and spread it evenly – this is best done with your fingers. Then again cut off any excess dough.
The onion tart gets a special kick if you grate a wafer-thin layer of Parmigiano Reggiano over it, but of course this is not the traditional method. However, this is how we do it ourselves.
The oven is preheated to 190 °C, without fan. Then the onion tart bakes at a medium height for around 45 minutes. It is ready when the edges of the pastry have turned a bronze colour.
The onion tart now needs to rest and cool a little, it tastes best lukewarm. However, it can also be enjoyed cold and reheated in the days that follow.
Enjoy.
And may the taste be with you.
Ingredients (for one deep baking tray):
For the dough:
1 cube of yeast (42 g) or 14 g dry yeast
½ tsp sugar
180 ml milk
500 g standard flour
1 level teaspoon of salt
30 g butter (optional)
For the filling:
1.5 kg onions
120 g smoked bacon
2 tsp neutral oil (alternatively: 50 g butter)
2 tsp icing sugar (optional)
2 tsp standard flour
380 g sour cream
380 g cream
3 eggs
1.5 tsp salt
Grated nutmeg
2 tsp ground caraway
Also:
3 tsp butter for the baking tray
Some grated Parmigiano Reggiano (optional)
