Zwiebelrostbraten With Crispy Onions and Buttery Potatoes

Imperial October 25, 2026October 25, 2026

Quick Recipe Version (TL;DR)

Yield: 4 servings
Prep Time: 25 minutes
Cook Time: 50 minutes
Total Time: 1 hour 15 minutes

Quick Ingredients

Beef: 4 boneless strip steaks, 200 g each and 2.5 cm thick; 30 ml neutral oil; ½ teaspoon fine salt; ¼ teaspoon ground black pepper.
Crisp onions: 600 g peeled yellow onions, thinly sliced; 75 g all-purpose flour; 30 g cornstarch; 500 ml neutral frying oil; ¼ teaspoon fine salt.
Pan sauce: 10 g tomato paste, 120 ml dry red wine, 360 ml low-sodium beef stock, 5 g Dijon mustard, 3 g cornstarch mixed with 15 ml cold water, 20 g cold unsalted butter, and ¼ teaspoon ground black pepper.
Buttery potatoes: 1 kg Yukon Gold potatoes, 2 liters water, 50 g unsalted butter, 1¼ teaspoons fine salt divided, and 8 g chopped flat-leaf parsley.

Do This

1. Heat the oven to 80°C (176°F). Slice the onions 2 mm thick, cut the potatoes into 4 cm pieces, and pat the steaks dry.
2. Cover the potatoes with 2 liters cold water, add 1 teaspoon salt, bring to a boil, and simmer for 15–18 minutes until tender.
3. Heat the frying oil to 170°C (338°F). Toss the onions with flour and cornstarch in four batches, frying each batch for 4–5 minutes. Drain on a rack, salt, and keep warm uncovered.
4. Drain the potatoes, steam-dry for 2 minutes, and toss with 50 g butter, ¼ teaspoon salt, and parsley. Cover and keep warm.
5. Season the beef and sear in 30 ml oil, working in two batches, for 3–4 minutes per side or until the centers reach 63°C (145°F). Rest for at least 3 minutes.
6. In the steak pan, cook the tomato paste for 30 seconds. Add wine and reduce for 2 minutes; add stock and mustard and simmer for 4 minutes. Add the cornstarch slurry and simmer for 1 minute, then whisk in 20 g cold butter off the heat.
7. Spoon sauce around the steaks, pile the crisp onions generously on top, and serve with the buttery potatoes.

Why You’ll Love This Recipe

A proper onion crown: A generous tangle of golden, crisp onions makes every bite special.
Tender beef without guesswork: A hot pan and a meat thermometer help you cook the steaks confidently.
Big flavor from one skillet: The browned steak drippings become a glossy red wine and beef pan sauce.
Comforting and complete: Buttery parsley potatoes round out this home-cooked take on the Austrian and southern German classic.

Grocery List

Meat: 4 boneless strip steaks, 200 g each and 2.5 cm thick.
Produce: 600 g yellow onions, weighed after peeling; 1 kg Yukon Gold potatoes; 1 small bunch flat-leaf parsley.
Dairy: 70 g unsalted butter.
Pantry: All-purpose flour, cornstarch, neutral high-heat oil such as sunflower or canola, tomato paste, dry red wine, low-sodium beef stock, Dijon mustard, fine salt, and ground black pepper.

Full Ingredients

For the Beef

4 boneless strip steaks, 200 g each, approximately 2.5 cm thick, with thick exterior fat trimmed
½ teaspoon fine salt, 3 g
¼ teaspoon ground black pepper
30 ml neutral high-heat oil, 2 tablespoons

For the Crisp Onions

600 g yellow onions, weighed after peeling, sliced into 2 mm rings or half-moons
75 g all-purpose flour
30 g cornstarch
500 ml neutral high-heat oil, for frying; most will remain in the pan
¼ teaspoon fine salt, 1.5 g

For the Rich Pan Sauce

10 g tomato paste, 2 teaspoons
120 ml dry red wine
360 ml low-sodium beef stock
5 g Dijon mustard, 1 teaspoon
3 g cornstarch, 1 teaspoon
15 ml cold water, 1 tablespoon
20 g cold unsalted butter, cut into small cubes
¼ teaspoon ground black pepper
Any juices collected from the resting steaks

For the Buttery Potatoes

1 kg Yukon Gold potatoes, peeled and cut into evenly sized 4 cm pieces
2 liters cold water
1 teaspoon fine salt, 6 g, for the cooking water
50 g unsalted butter, cut into pieces
¼ teaspoon fine salt, 1.5 g, for finishing
8 g finely chopped flat-leaf parsley, approximately 2 tablespoons

Zwiebelrostbraten With Crispy Onions and Buttery Potatoes – Closeup

Step-by-Step Instructions

Step 1: Prepare the ingredients and warming oven

Heat the oven to 80°C (176°F). Set a wire rack over a rimmed baking sheet for the fried onions. Have a heavy, high-sided saucepan, a potato pot, and a large heavy skillet ready; a 30 cm stainless-steel or cast-iron skillet works well for the steaks.

Slice the onions into 2 mm rings or half-moons, separate the layers, and pat them thoroughly dry. Peel and cut the potatoes into 4 cm pieces. Pat the steaks dry with paper towels and trim away any thick, hard exterior fat. Measure the sauce ingredients so they are ready when the steaks leave the pan.

Step 2: Simmer the potatoes until tender

Put the potatoes in a large pot with 2 liters cold water and 1 teaspoon fine salt. The water should cover them by approximately 2 cm. Bring to a boil over high heat, then reduce the heat to maintain a gentle simmer.

Cook for 15–18 minutes after the water reaches a boil, until a small knife slides easily into the centers. Start checking at 15 minutes so the potatoes stay intact rather than becoming waterlogged. Fry the onions while the potatoes cook.

Step 3: Fry the onions in small batches

Pour 500 ml oil into a heavy, high-sided saucepan approximately 20 cm wide. The oil should occupy no more than one-third of the pan. Heat it to 170°C (338°F), checking with a frying thermometer.

Mix the flour and 30 g cornstarch in a wide bowl. Divide the onions into four equal batches of approximately 150 g. Just before frying each batch, toss it in the flour mixture and shake off the excess. Do not coat all the onions in advance, or the coating will become damp.

Carefully lower one batch into the oil and fry for 4–5 minutes, gently separating and turning the strands with a slotted spoon. Remove them when evenly golden; they will darken slightly as they cool. Let the oil return to 170°C before adding the next batch.

Transfer the onions to the prepared rack and sprinkle with the ¼ teaspoon salt, dividing it among the batches. Keep the finished onions uncovered in the warming oven. A rack keeps air moving underneath so the coating stays crisp.

Step 4: Butter the potatoes and keep them warm

Drain the cooked potatoes thoroughly, then return them to the empty pot over low heat for 2 minutes, shaking the pot gently to release excess moisture.

Remove from the heat and add 50 g butter, ¼ teaspoon fine salt, and the chopped parsley. Fold gently until the butter melts and coats the potatoes. Transfer to a covered oven-safe dish and keep warm in the 80°C oven while you cook the beef.

Step 5: Sear the steaks and let them rest

Season the steaks on both sides with ½ teaspoon fine salt and ¼ teaspoon pepper. Heat the large skillet over medium-high heat for 2 minutes. Add 15 ml of the searing oil; it should shimmer without smoking heavily.

Add two steaks, leaving space between them. Sear for 3–4 minutes per side, turning once, until well browned and the centers reach 63°C (145°F). Insert an instant-read thermometer horizontally into the center of each steak; thickness and pan heat affect the exact cooking time.

Transfer to a warm plate and loosely tent with foil. Add the remaining 15 ml oil and repeat with the other two steaks. Let every steak rest for at least 3 minutes before serving; they can rest while you make the sauce. Keep the browned bits in the skillet, but pour off excess fat, leaving approximately 1 tablespoon.

Step 6: Build the pan sauce

Reduce the skillet heat to medium. Add the tomato paste and stir for 30 seconds, until it darkens slightly. Pour in the red wine carefully and scrape up the browned bits with a wooden spoon. Simmer for 2 minutes, until the wine has reduced by about half.

Add the beef stock and Dijon mustard. Simmer for 4 minutes, stirring occasionally, until the sauce tastes concentrated. The browned steak drippings should dissolve into the sauce; discard any black, burned pieces rather than scraping them in.

Step 7: Finish the sauce until glossy

Stir together the 3 g cornstarch and 15 ml cold water until smooth, then whisk the mixture into the simmering sauce. Cook for 1 minute, stirring, until it lightly coats the back of a spoon.

Remove the skillet from the heat. Add the resting steak juices and ¼ teaspoon pepper, then whisk in the 20 g cold butter a few pieces at a time. The finished sauce should be glossy and pourable. Do not boil it after adding the butter.

Step 8: Plate with a generous onion crown

Divide the buttery potatoes among four warm plates. Add one steak to each plate and spoon the rich pan sauce around the beef, letting a little run beneath it.

Finish each steak with one-quarter of the crisp onions, piling them high. Keep the sauce underneath or beside the onions so their delicate coating stays crunchy. Serve immediately.

Pro Tips

Choose tender steaks: Boneless strip steak, also called striploin, is a dependable home-cook choice. Avoid substituting an un-tenderized braising cut, which will not soften during this quick cooking method.
Thin, dry onions fry best: Even 2 mm slices cook consistently. If using a mandoline, use its hand guard, and dry the slices well before coating.
Watch the oil temperature: Cool oil makes greasy onions; overheated oil browns the coating before the onions become crisp. Let it recover between batches.
Protect the flavorful pan drippings: If the skillet begins smoking aggressively, reduce the heat slightly. Deep brown is delicious; blackened drippings can make the sauce bitter.
Use temperature, not color alone: The cooking times are a guide. For food safety, cook the steaks to 63°C (145°F) and rest them for at least 3 minutes.

Variations

Wine-free sauce: Replace the 120 ml red wine with 120 ml additional low-sodium beef stock. Follow the same reduction steps and stir in 5 ml red wine vinegar just before adding the butter.
Swabian-style side: Replace the potatoes with 600 g cooked Spätzle tossed with 30 g butter. Keep the beef, onions, and sauce unchanged.
Extra-crisp onion coating: Replace the 75 g all-purpose flour with 75 g white rice flour, keeping the 30 g cornstarch. This changes the onion coating only; check all other ingredients separately if avoiding gluten.

Storage & Make-Ahead

Make ahead: Slice the onions up to 1 day ahead, refrigerate them in a covered container, and pat them dry before coating. Peel and cut the potatoes up to 1 day ahead and refrigerate them submerged in cold water; drain and use fresh measured water for cooking. The steaks and onions are best cooked close to serving.

Store: Refrigerate leftover beef, sauce, potatoes, and onions in separate covered containers within 2 hours. Use within 3–4 days, although the onions have the best texture within 1 day.

Reheat: Warm the beef and sauce gently in a covered skillet, adding 15–30 ml water if needed, until leftovers reach 74°C (165°F); reheated steak will be more well done. Reheat covered potatoes at 180°C (356°F) for approximately 20 minutes, until they reach 74°C. Recrisp onions separately on a rack at 180°C (356°F) for 5–7 minutes, watching closely to prevent burning.

Nutrition (per serving)

Estimated for one steak with one-quarter of the onions, sauce, and potatoes. The estimate assumes approximately 60 ml of frying oil is absorbed across the full recipe; actual absorption and coating retention vary.