Peruvian Steak Stir-Fry with French Fries

Peruvian steak stir-fry with French fries, commonly known as lomo saltado, combines seared beef, red onion, tomato, soy sauce, and vinegar in a hot, savory pan. The fries are folded in at the end, so they catch the tangy sauce while keeping some crisp edges; this version uses oven-baked fries for an easy home-cook method.

Lomo saltado is a well-known Peruvian-Chinese, or chifa, dish, and home versions vary in their vegetables, seasonings, and how the fries are served. This recipe keeps the signature beef, onion, tomato, and fries together, with aji amarillo for a gently fruity chile note when available.

Ingredients

1 lb (450 g) frozen straight-cut French fries
1¼ lb (565 g) sirloin steak, trimmed and cut across the grain into strips about ¾ inch (2 cm) thick
1½ tbsp (22 ml) neutral oil, such as canola or avocado oil, divided
1 tbsp (15 ml) soy sauce
1 tbsp (15 ml) red wine vinegar
1 tsp (5 ml) aji amarillo paste, optional but traditional in many versions
½ tsp (2.5 g) ground cumin
½ tsp (2.5 g) fine salt, plus more to taste
¼ tsp (1 g) black pepper
1 medium red onion, about 8 oz (225 g), cut into thick wedges
2 medium plum tomatoes, about 8 oz (225 g), cut into wedges and seeded if very watery
2 garlic cloves, about 6 g, finely chopped
1 tbsp (15 ml) water
2 tbsp (8 g) chopped fresh cilantro leaves and tender stems
2 medium scallions, about 30 g, thinly sliced, optional
4 lime wedges, about 1 lime (60 g), for serving

Instructions

Prepare the ingredients. Heat the oven to the temperature listed on the fries package, using 425°F (220°C) if the package gives a range. Pat the steak dry, slice it across the grain, and set it on a plate. In a small bowl, stir together the soy sauce, vinegar, aji amarillo paste, cumin, salt, and black pepper. Cut the onion and tomatoes, chop the garlic and cilantro, and keep the ingredients close to the stove. This preparation takes about 20 minutes and helps the quick stir-fry move smoothly.
Bake the fries. Spread the frozen fries in a single layer on a rimmed baking sheet, leaving room around them so hot air can circulate. Bake for 25 minutes, turning them once about halfway through, or follow the package timing if it differs. They should be browned and crisp at the edges. Keep them on the tray while you cook the beef and vegetables; do not cover them, because trapped steam softens the crust.
Sear the beef. Heat a large wok or heavy skillet over high heat until very hot, then add 1 tablespoon (15 ml) of the oil. Add the steak in a single layer, working in two batches if the pan is crowded. Let the pieces sear briefly before turning, then stir-fry until browned on the outside and cooked through, about 3–5 minutes per batch depending on thickness. Check a thick piece with a food thermometer inserted from the side: USDA FSIS guidance sets 145°F (63°C) as the safe minimum for whole cuts of beef, followed by a 3-minute rest. Transfer the cooked steak to a clean plate and let it rest for 3 minutes. Avoid returning it to the raw-meat plate.
Cook the vegetables. Add the remaining ½ tablespoon (7 ml) oil to the hot pan. Add the onion and stir-fry for about 2 minutes, keeping the wedges fairly intact. Add the garlic and cook for 20–30 seconds, just until fragrant. Add the tomato wedges and cook for about 1 minute; they should warm and soften slightly without collapsing into a sauce.
Make the quick pan sauce. Pour the soy-vinegar mixture and 1 tablespoon (15 ml) water into the pan. Stir and scrape up the browned bits for about 30 seconds. Taste a little of the sauce before adding more salt, since soy sauce can be salty. If the pan looks dry, add another teaspoon of water; the goal is a light coating, not a pool of liquid.
Combine and serve promptly. Return the rested beef and any juices on its plate to the pan, then add the hot fries. Toss gently for about 30 seconds, just long enough to coat some of the fries without breaking them up. Fold in the cilantro and scallions, if using. Serve immediately with lime wedges and, if desired, rice alongside.

Tips

Keep the pan hot and uncrowded. A crowded pan releases moisture and steams the beef instead of browning it. Cook the steak in batches if needed, and let the pan heat back up before adding the next batch. A wide skillet works if you do not have a wok.
Cut across the grain. Look for the direction of the long muscle fibers and slice across them. That makes the beef easier to chew. Strips of similar thickness also cook at a more even pace, which helps when checking a representative piece with a thermometer.
Choose a practical aji amarillo substitute. Aji amarillo paste is sold in many Latin American grocery shops and some supermarkets. If you cannot find it, use 1 tablespoon (15 g) finely minced yellow bell pepper plus a small pinch of cayenne; the result will be milder and less fruity. Do not add a whole hot chile unless you want noticeably more heat.
Keep fries crisp until the last moment. Bake them until browned, leave them uncovered, and toss them with the sauce only just before serving. If you prefer very crisp fries, serve them beside the beef instead of mixing them into the pan.

Serving Suggestions

Serve the stir-fry as soon as it is tossed, while the beef is hot and the fries still have crisp edges. Steamed white rice is a classic companion: it catches the savory juices and makes the meal more substantial. Put lime wedges on the table so each person can brighten their portion to taste. A simple green salad with lettuce, cucumber, or avocado provides a cool contrast without competing with the strong soy-vinegar flavor.

For a family-style meal, bring the skillet to the table if it is safe to do so, or transfer everything to a warm shallow platter. Keep the beef, onion, and tomato visible rather than burying them under the fries. A small bowl of extra chopped cilantro or sliced scallions lets diners add a fresh finish. If serving rice, offer it in separate bowls rather than mixing it into the pan; this preserves the texture of the fries and lets everyone choose their preferred balance.

Variations

Serve the fries on the side. This is the easiest way to preserve their crunch, especially if dinner may sit on the table for a few minutes. Cook the beef and vegetables as directed, then spoon them over or beside a portion of fries. Add a little sauce to the beef but avoid soaking the potatoes.

Use fresh-cut potatoes. Cut about 1 lb (450 g) russet potatoes into fries, rinse off excess surface starch, and dry them very thoroughly before baking with 1 tablespoon (15 ml) oil and a pinch of salt. Bake in a single layer at 425°F (220°C), turning once, until golden and cooked through; the time varies with thickness, usually around 30–40 minutes. This takes longer than frozen fries, so start them earlier and keep the rest of the recipe’s timing separate.

Adjust the heat. Omit the aji amarillo for a mild version, or add a little more paste for a stronger fruity chile flavor. A minced jalapeño can stand in for some of the heat, but it tastes greener and sharper than aji amarillo. Add chiles gradually, since their heat varies.

Change the protein. Thin strips of pork tenderloin can be used in place of beef, but cook them to the safe temperature for whole cuts of pork: 145°F (63°C), followed by a 3-minute rest. For a meat-free dinner, use thick strips of seared mushrooms; they will brown and absorb the sauce, though the dish will no longer have the traditional beef character. Cook any substitute separately as needed so the pan does not become crowded.

Storage and Reheating

This dish is best freshly made because the fries soften as they absorb sauce. Refrigerate leftovers within 2 hours of cooking, in a covered shallow container, and use them within 3–4 days. For the best texture, store any fries that have not yet been mixed separately from the beef and vegetables. If everything has already been tossed together, it is still safe to refrigerate and reheat as directed, but expect the potatoes to be softer.

Reheat leftovers in a skillet over medium heat with a splash of water, stirring until steaming hot throughout; a food thermometer should read 165°F (74°C) for reheated leftovers. The microwave also works: cover loosely, heat in short intervals, and stir between intervals so the center warms evenly. The fries will not regain their original crispness in the microwave. For a better finish, spread the reheated mixture on a baking sheet and warm it in a 400°F (200°C) oven until hot, checking that the center reaches 165°F (74°C). Do not leave cooked leftovers at room temperature for more than 2 hours.

Frequently Asked Questions

What cut of steak works best?
Sirloin is a good balance of flavor, tenderness, and price, and it is easy to slice into even strips. Flank steak or skirt steak can also work; slice either one thinly across the grain. Avoid very thin pre-sliced beef if it tends to overcook before you can check it safely.

Can I make this without a wok?
Yes. Use the widest heavy skillet you have, preferably one that holds heat well. Cook the beef in batches instead of piling it into the pan, and use high heat with good ventilation. A wok is convenient, but it is not essential for a successful stir-fry.

Can I prepare any part ahead?
You can mix the sauce, chop the onion and garlic, and cut the tomatoes a few hours ahead; cover and refrigerate them separately. The steak can also be sliced shortly before cooking and kept covered in the refrigerator. Bake the fries and stir-fry the beef close to mealtime so the potatoes do not sit in sauce and turn soft.

Why did my beef turn out tough?
Common causes are slicing with the grain, using a pan that is not hot enough, overcrowding the pan, or cooking thin pieces for too long. Slice across the fibers, sear in small batches, and check a thick strip with a thermometer. The required 3-minute rest after the safe minimum temperature also helps the juices settle before the beef goes back into the pan.

Can I use fresh tomatoes instead of plum tomatoes?
Yes. Choose firm tomatoes and cut them into wedges. If they are especially juicy, remove some of the seeds and gel before cooking so the pan sauce stays concentrated. Add the tomatoes near the end and cook them only until warmed and slightly softened; extended cooking can make them release more liquid and lose their shape.

Is the dish supposed to be saucy?
It should have enough light sauce to season the beef and vegetables, but it is not meant to resemble a stew. The vinegar and soy sauce create a concentrated coating, and the tomatoes add a little moisture. If your pan contains a lot of liquid, lift the beef and vegetables out briefly and simmer the sauce for a short time before tossing everything together.

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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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