Polish Onion Soup with Rye Bread and Marjoram

Polish onion soup, or zupa cebulowa, is a comforting broth-based soup built around slowly softened onions, with marjoram adding a gentle herbal note. This home-style version is served with toasted rye bread, and its simple ingredients let the onions bring sweetness and depth without making the soup heavy. Recipes vary, so think of this as a practical Polish-style bowl rather than a single definitive version.

Ingredients

3 lb (1.36 kg) yellow onions, peeled and thinly sliced, about 8 cups
4 tbsp (57 g) unsalted butter
1 tbsp (15 ml) neutral oil, such as canola or sunflower oil
2 garlic cloves (about 6 g), finely chopped
2 tbsp (16 g) all-purpose flour
8 cups (1.9 L) low-sodium beef broth or vegetable broth
1 dried bay leaf
1 tsp (1 g) dried marjoram
½ tsp (1 g) freshly ground black pepper
1 tsp (5 g) fine salt, plus more to taste
1 tsp (5 ml) apple cider vinegar
6 slices (about 240 g) rye bread, each about ½ inch thick
1½ cups (150 g) grated mild melting cheese, such as gouda, optional

Yellow onions are the dependable choice here: they become sweet and mellow as they cook, while still tasting like onions rather than turning candy-sweet. Low-sodium broth gives you room to season the finished soup accurately. Beef broth makes a fuller, more traditional-style savory base; vegetable broth works well for a meat-free pot. The cheese is optional, since rye toast on its own is a satisfying accompaniment.

Instructions

Prepare the vegetables and bread. Peel the onions, cut them in half from root to tip, and slice them thinly. Chop the garlic and measure out the remaining ingredients. This takes about 20 minutes, depending on your knife speed. If the onion slices vary slightly in thickness, that is fine; just keep them reasonably even so they soften at a similar pace.
Soften and brown the onions. Set a large, heavy-bottomed pot over medium-low heat. Add the butter and oil. Once the butter has melted, add the onions and salt, then stir to coat. Cook uncovered for 35 minutes, stirring every few minutes and more often as the onions begin to shrink and color. Keep the heat moderate: the goal is tender onions with deep golden patches, not scorched edges. If brown bits collect quickly on the bottom, lower the heat and stir them into the onions.
Add the garlic. Stir in the chopped garlic and cook for 1 minute, just until fragrant. Avoid letting it brown, since burnt garlic can make the broth taste bitter.
Thicken lightly. Sprinkle the flour evenly over the onions and stir for 2 minutes. The flour should disappear into the buttery onion mixture and cook briefly; this helps give the soup a little body without making it as thick as gravy. Scrape the bottom of the pot as you stir.
Simmer the soup. Pour in the broth gradually while stirring so the flour does not form lumps. Add the bay leaf, marjoram, and black pepper. Bring the pot to a gentle simmer, which should take about 3 minutes, then simmer uncovered for 25 minutes. Stir once or twice. The onions should be very tender and the broth lightly thickened. Remove the bay leaf, stir in the vinegar, and taste. Add more salt or pepper only if needed; broth brands vary in saltiness.
Toast the rye bread. During the last 6 minutes of simmering, toast the rye slices in a dry skillet over medium heat for about 2 to 3 minutes per side, until crisp and browned. If using cheese, scatter it over the bread during the last minute and cover the skillet briefly so it melts. Keep an eye on the slices, since rye bread can go from toasted to dark quickly.
Serve hot. Ladle the soup into six bowls and serve each portion with a slice of toasted rye bread, either alongside or set on top. For the best texture, add the bread just before eating rather than leaving it in the soup while it waits at the table.

Tips

Give the onions enough time. The long, gentle cook is what gives this soup its rounded flavor. If the onions are still pale and firm at 35 minutes, cook them a little longer rather than raising the heat sharply. A crowded pot can take longer, and frequent stirring helps prevent uneven browning.
Choose the broth to suit the meal. Beef broth creates a deeper, more robust soup, while vegetable broth keeps it meat-free and lighter. If you only have regular-sodium broth, begin with less added salt and adjust after simmering.
Use a substitute for the flour if needed. For a gluten-free pot, leave out the flour and mix 1 tbsp (8 g) cornstarch with 2 tbsp (30 ml) cold water. Stir the slurry into the simmering soup and cook for 1 to 2 minutes until slightly thickened. The result is a little glossier and less traditionally flour-rounded, but still works well.
Keep the bread separate. Rye toast softens rapidly in hot soup. Toast only what you plan to serve, and store extra bread separately so leftovers remain soup rather than becoming a thick bread stew.

Serving Suggestions

Serve the soup as a light main course with one or two slices of rye bread per person, or offer smaller bowls as a first course before roasted vegetables, pierogi, or a simple meat-and-potato meal. A crisp salad of cabbage, cucumber, or leafy greens gives the meal freshness and crunch. Keep the side dishes fairly plain: the soup already has a deep, savory onion flavor, and heavily seasoned accompaniments can compete with it.

For a more substantial bowl, place the toasted bread at the bottom of each serving bowl and ladle soup over it just before eating. This makes a softer, broth-soaked toast, while serving the toast on the side keeps it crisp. Pass extra black pepper at the table. If you use the optional cheese, the toast adds richness, so you may prefer a smaller portion of bread or a sharper salad alongside.

Variations

Make it vegetarian: Use vegetable broth and check that the bread and any cheese suit your needs. A well-flavored vegetable stock brings enough savoriness for the onions to remain the focus. For extra depth, cook the onions slowly until fully golden rather than relying on a stronger broth.

Use a different bread: Dense whole-grain bread or sourdough can stand in for rye. Rye gives the bowl a distinctly earthy, slightly tangy accompaniment; sourdough tastes sharper, while whole-grain wheat is milder. Toast whichever bread you choose so it can hold up beside the hot soup.

Make it without cheese: The soup does not depend on a cheese topping. Skip it for a simpler finish, or add a small spoonful of chopped fresh parsley to each bowl for color. Parsley changes the flavor toward a fresher, greener finish, while the marjoram remains the main herb in the recipe.

Adjust the texture: For a more rustic soup, leave the onions in long strands. For a smoother, thicker bowl, blend only a portion of the soup and stir it back into the pot. Avoid blending the whole pot unless you specifically want a puréed texture; keeping some onion pieces gives the soup its characteristic home-style feel.

Storage and Reheating

Cool leftovers promptly and refrigerate them within 2 hours of cooking, in a covered container. The soup keeps for 3 to 4 days in the refrigerator. Store the rye bread and cheese separately; toast fresh bread when serving so it does not absorb the broth in storage. If the soup thickens as it chills, loosen it with a splash of water or broth while reheating.

Reheat only the portion you need in a saucepan over medium heat, stirring occasionally, until steaming throughout and at least 165°F (74°C), the USDA FSIS safe temperature for reheated leftovers. You can also microwave a covered, microwave-safe bowl, stirring halfway through and checking that the center reaches 165°F (74°C). Freeze the soup without bread for up to 2 to 3 months for best quality. Thaw it in the refrigerator overnight, then reheat to 165°F (74°C); the onions may soften further, but the flavor will remain good.

Frequently Asked Questions

What makes this Polish onion soup different from French onion soup?
Recipes for both soups vary, but this version leans on a clear broth, marjoram, and rye bread rather than a thick layer of cheese melted over a bowl. The onions are still cooked slowly for depth. Treat the differences as a style of preparation, not a strict rule: home recipes in both cuisines have many variations.

Can I make Polish onion soup ahead of time?
Yes. Make the soup up to 3 days ahead, cool it promptly, and refrigerate it in a covered container. Reheat it gently to at least 165°F (74°C), then toast the bread just before serving. Keeping the topping separate preserves its crispness and makes the soup easier to store.

Why are my onions taking longer to brown?
Onions release plenty of moisture, and a large quantity can initially steam before it begins to brown. Continue cooking over medium-low heat, stir regularly, and allow the moisture to evaporate. A pot with a wide base helps; a very high flame is not a shortcut, because it can burn the onions before they soften.

Can I leave out the flour?
Yes. The soup will be thinner but still flavorful, especially if you cook the onions until very tender. For a closer match to the lightly thickened version, use the cornstarch slurry in the Tips section. Add it gradually and stop when the broth has the texture you like.

Which onions and broth should I use?
Yellow onions are the most versatile option, but white onions also work and may taste a little sharper. Sweet onions can be used, though the finished soup will have a sweeter profile. Choose low-sodium beef broth for a deeper savory base or vegetable broth for a meat-free version, then season at the end.

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Safety notes: safe minimum internal temperatures from USDA FSIS; raw and undercooked fish guidance from the U.S. FDA. Food safety notes

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