Although it translates to onion cake, German zwiebelkuchen is better described as a savory onion pie. The base of the dish is a thin, buttery crust that is usually made with yeasted dough. The center of the pie is filled with a combination of caramelized onions, smoky bacon, and a creamy mixture of eggs and sour cream.
The pie is usually spiced with salt, pepper, and caraway seeds, which give the dish a deep and earthy flavor. Even though there are several varieties of zwiebelkuchen, it is traditionally baked as a round deep-dish pie. In the past, this savory delicacy was made with sour milk and plain bread dough–common staples in many German households.