Quick Recipe Version (TL;DR)
Quick Ingredients
- 4 cups (500 g) all-purpose flour
- 1 packet (2 1/4 tsp; 7 g) instant or active dry yeast
- 1 1/4 cups (300 ml) warm water, 105–110°F
- 1 large egg
- 3 tbsp unsalted butter, melted; plus 2 tbsp olive oil for pan
- 2 tsp kosher salt + 1 tsp sugar
- 8 oz (225 g) thick-cut bacon, cut into lardons
- 3 lb (1.36 kg) yellow onions, thinly sliced
- 2 tbsp unsalted butter (for onions)
- 1 1/2 tsp caraway seeds, plus 1/2 tsp for topping
- 1/2 cup (120 ml) dry white wine
- 3 large eggs (for custard)
- 1 cup (240 g) crème fraîche
- 1/2 cup (120 ml) whole milk
- 1 tsp kosher salt, 1/2 tsp black pepper, pinch nutmeg
- Chives or parsley, for garnish
Do This
- 1. Make dough: Bloom yeast in warm water with sugar. Mix in flour, salt, egg, and melted butter; knead until smooth. Rise 60–75 minutes.
- 2. Render bacon in a large skillet; remove and reserve 1/3 for topping. Add butter and onions; cook low and slow 40–50 minutes.
- 3. Season onions with salt, pepper, caraway; deglaze with wine and cook off. Cool 10 minutes.
- 4. Whisk custard: eggs, crème fraîche, milk, salt, pepper, nutmeg.
- 5. Oil a 18×13-inch rimmed sheet pan; stretch dough to fit. Rest 10 minutes; finish stretching. Dock and rise 20–25 minutes. Preheat oven to 425°F (220°C).
- 6. Assemble: spread onions, pour custard, scatter reserved bacon and caraway. Bake 25–30 minutes until golden and set. Rest 10 minutes; garnish and serve warm.
Why You’ll Love This Recipe
- Classic German comfort: tender yeast crust, silky onions, and savory bacon in a creamy custard.
- Sheet-pan friendly: feeds a crowd with minimal fuss and sturdy, sliceable squares.
- Balanced flavors: gentle caraway warmth, a hint of white wine brightness, and rich crème fraîche.
- Great warm or room temp: perfect for fall gatherings, Oktoberfest, or Sunday brunch.
Grocery List
- Produce: 3 lb yellow onions, fresh chives or parsley, 2 garlic cloves (optional)
- Dairy: Crème fraîche, whole milk, unsalted butter, eggs
- Pantry: All-purpose flour, instant or active dry yeast, sugar, kosher salt, black pepper, caraway seeds, olive oil, dry white wine, nutmeg, thick-cut bacon
Full Ingredients
For the Yeasted Crust
- 4 cups (500 g) all-purpose flour
- 1 packet (2 1/4 tsp; 7 g) instant or active dry yeast
- 1 1/4 cups (300 ml) warm water (105–110°F / 40–43°C)
- 1 large egg
- 3 tbsp (42 g) unsalted butter, melted and cooled slightly
- 2 tsp kosher salt
- 1 tsp sugar
- 2 tbsp olive oil, for the pan
For the Onion-Bacon Topping
- 8 oz (225 g) thick-cut bacon, cut into 1/4-inch lardons
- 3 lb (1.36 kg) yellow onions, halved root-to-stem and thinly sliced
- 2 tbsp unsalted butter
- 1 1/2 tsp caraway seeds, lightly crushed
- 1/2 cup (120 ml) dry white wine (Riesling or Pinot Blanc), optional but recommended
- 1 tsp kosher salt, plus more to taste
- 1/2 tsp freshly ground black pepper
For the Crème-Fraîche Custard
- 3 large eggs
- 1 cup (240 g) crème fraîche
- 1/2 cup (120 ml) whole milk
- 1 tsp kosher salt
- 1/2 tsp freshly ground black pepper
- Pinch freshly grated nutmeg
To Finish
- 1/2 tsp caraway seeds, for sprinkling
- 2 tbsp chopped fresh chives or parsley
- Flaky sea salt, to taste (optional)
Step-by-Step Instructions
Step 1: Make a soft, springy dough
In the bowl of a stand mixer (or a large mixing bowl), whisk warm water and sugar, then sprinkle in the yeast. Let stand 5 minutes until foamy (if using instant yeast, you can skip the wait and proceed). Add flour, salt, egg, and melted butter. Mix on low until a shaggy dough forms, then knead on medium speed 6–8 minutes (or by hand 8–10 minutes) until smooth and elastic. The dough should be soft but not sticky; add 1–2 tbsp water or flour as needed to reach a supple consistency.
Step 2: First rise
Shape the dough into a ball and place in a lightly oiled bowl. Cover and let rise in a warm spot until doubled in size, 60–75 minutes. While the dough rises, start the topping.
Step 3: Render bacon
Place bacon lardons in a large wide skillet (12 inches) over medium heat. Cook, stirring occasionally, until the fat renders and the bacon is just crisp, 8–10 minutes. Using a slotted spoon, transfer bacon to a paper towel–lined plate. Reserve about one-third of the bacon for topping later; the remaining two-thirds will mix into the onions. Leave 2–3 tbsp bacon fat in the pan (pour off excess if needed).
Step 4: Slow-caramelize the onions with caraway
Add 2 tbsp butter to the skillet with the bacon fat, then add the sliced onions and 1 tsp salt. Cook over medium heat for 10 minutes, stirring to wilt. Reduce heat to medium-low and continue to cook, stirring every few minutes, until soft, golden, and sweet but not deeply browned, 30–40 minutes more. If the pan looks dry or onions threaten to scorch, add a splash of water. Stir in 1 1/2 tsp lightly crushed caraway and the reserved two-thirds of the bacon. Increase heat to medium, pour in the white wine to deglaze, scraping up browned bits, and simmer until the liquid is fully evaporated, 2–3 minutes. Season with black pepper. Let cool 10 minutes so the custard will not curdle upon assembly.
Step 5: Mix the crème-fraîche custard
In a medium bowl, whisk together eggs, crème fraîche, milk, 1 tsp salt, 1/2 tsp black pepper, and a pinch of nutmeg until smooth. If your crème fraîche is very thick, whisk it first to loosen before adding the milk; tiny lumps are fine and will melt in the oven.
Step 6: Shape the crust on a sheet pan
Heat the oven to 425°F (220°C) with a rack in the lower-middle position. Lightly oil a rimmed half-sheet pan (18×13 inches) with 2 tbsp olive oil. Turn the risen dough onto the pan and gently press and stretch it toward the corners. If it resists, let it relax 10 minutes, then finish stretching to fill the pan in an even layer. Dock the dough all over with a fork to prevent large bubbles. Loosely cover and let rise 20–25 minutes until slightly puffy.
Step 7: Assemble the Zwiebelkuchen
Spread the cooled onion-bacon mixture evenly over the dough, right up to the edges. Whisk the custard briefly and pour it evenly over the onions. Sprinkle the reserved crisp bacon over the surface and finish with 1/2 tsp caraway seeds.
Step 8: Bake until golden, then rest and serve
Bake at 425°F (220°C) for 25–30 minutes, rotating the pan halfway through, until the crust edges are deep golden, the custard is set in the center, and the top has light toasty spots. If desired, broil for 1–2 minutes to further brown the top—watch closely. Cool on a rack for 10 minutes. Scatter with chopped chives or parsley and a pinch of flaky salt. Cut into 12 squares and serve warm.
Pro Tips
- Onion doneness matters: aim for soft, golden, and sweet, not dark jammy brown—too dark can overpower the custard.
- Cool the onions slightly before assembly so the hot steam does not scramble the eggs in the custard.
- For extra lift, start the bake on a preheated baking steel or inverted sheet pan to crisp the bottom crust.
- Reserve some bacon to scatter on top so you get crisp pieces above and savory bits within the onion layer.
- Lightly crush caraway seeds between your fingers to release aroma without overwhelming the tart.
Variations
- Vegetarian: skip bacon; sauté onions in 3 tbsp butter and add 1/2 tsp smoked paprika for depth.
- Cheese lovers: sprinkle 1 cup (100 g) grated Gruyère or Emmental over the onions before the custard.
- Rye-blend crust: swap 1 cup (120 g) of the all-purpose flour with medium rye flour; increase water by 1–2 tbsp as needed.
Storage & Make-Ahead
Caramelize the onions (and cook bacon) up to 4 days ahead; refrigerate in airtight containers. The dough can be made the night before and cold-fermented: refrigerate after kneading, then bring to room temperature and continue with shaping (allow 60–90 minutes). Baked Zwiebelkuchen keeps refrigerated for 3 days; reheat at 350°F (175°C) for 12–15 minutes. Freeze cooled slices, well wrapped, up to 2 months; reheat from frozen at 350°F (175°C) for 18–22 minutes.
Nutrition (per serving)
Approximate: 450 calories; 24 g fat; 45 g carbohydrates; 15 g protein; 3 g fiber; 850 mg sodium.
