Lomo Saltado Sandwich With Tender, Savory Beef

A lomo saltado sandwich brings Peru’s stir-fried beef classic to a crusty roll, with tomatoes, red onion, and a tangy soy-vinegar sauce. It keeps the dish’s lively sweet-savory flavor and adds crisp fries for a filling, easy-to-eat meal.

Ingredients

1 lb (450 g) beef sirloin or flank steak, trimmed and cut across the grain into strips about ¼ inch (6 mm) thick
1 tsp (5 ml) kosher salt
½ tsp (1 g) freshly ground black pepper
2 tbsp (30 ml) neutral oil, such as canola or avocado oil, divided
1 medium red onion, about 8 oz (225 g), cut into thick wedges
2 medium Roma tomatoes, about 8 oz (225 g), cut into wedges
2 garlic cloves, finely chopped, about 2 tsp (6 g)
2 tbsp (30 ml) soy sauce
1 tbsp (15 ml) red wine vinegar
1 tsp (5 ml) Worcestershire sauce
1 tsp (5 g) aji amarillo paste, optional; use a little minced jalapeño or a pinch of red pepper flakes for heat, though the flavor will differ
1 tbsp (15 ml) water
8 oz (225 g) frozen thin-cut fries, or about 2 cups (225 g) cooked fries
4 crusty sandwich rolls, about 7 oz (200 g) each
¼ cup (60 g) mayonnaise
2 tbsp (8 g) chopped fresh cilantro
1 lime, cut into wedges, for serving

Instructions

Pat the beef dry, then season it with the salt and pepper. Keep the strips in a loose layer rather than packing them together; crowded beef steams and is less likely to brown.
Cook the fries according to the package directions, or bake or air-fry them until golden and crisp. Keep them warm while you make the beef. If using an oven, follow the package temperature and timing rather than adding the fries to the stir-fry.
Stir the soy sauce, red wine vinegar, Worcestershire sauce, aji amarillo paste, and water together in a small bowl. Set the sauce near the stove. Split the rolls and lightly toast them, if desired.
Heat 1 tablespoon (15 ml) oil in a large skillet or wok over high heat until shimmering. Add half the beef in a single layer and sear for about 1–2 minutes per side, turning once. Transfer it to a clean plate and repeat with the remaining beef and oil. For food safety, check the thickest strips with a food thermometer: USDA FSIS sets 145°F (63°C) with a 3-minute rest as the safe minimum for whole cuts of beef. Let the seared beef rest on the plate for 3 minutes.
Reduce the heat to medium-high. Add the onion to the skillet and cook for about 2 minutes, stirring occasionally, until it begins to soften but still has some bite. Add the tomatoes and garlic; cook for 1–2 minutes, just until the tomatoes start to release their juices. Avoid cooking them until they collapse.
Return the rested beef and any juices to the pan. Pour in the sauce and toss everything for 30–60 seconds, just until glossy and hot. Remove the pan from the heat; the vegetables should remain distinct, not turn into a stew.
Spread about 1 tablespoon (15 g) mayonnaise inside each roll. Divide the beef and vegetables among the rolls, spooning on a little pan sauce without soaking the bread. Add a portion of hot fries to each sandwich or serve them alongside. Finish with cilantro and lime wedges, and serve immediately.

Tips

Slice across the grain. Look for the direction of the muscle fibers and cut across them; this shortens the fibers and makes each bite easier to chew.
Use a hot, roomy pan. Sear in batches if needed. A crowded pan releases moisture, which prevents the beef from browning and can overcook it before it develops color.
Choose your vinegar thoughtfully. Red wine vinegar gives a clean tang. If unavailable, use distilled white vinegar in the same amount for a sharper taste, or rice vinegar for a milder result.
Keep the bread from going soggy. Toasting the cut sides and adding only a little sauce to the filling helps. Assemble the sandwiches just before serving, especially if fries are inside.

Serving Suggestions

Serve the sandwiches hot with extra fries, lime wedges, and a small dish of aji amarillo sauce or mayonnaise for dipping. A simple green salad, sliced avocado, or lightly dressed cabbage adds freshness without competing with the savory filling. For a more classic lomo saltado-style plate, serve the fries on the side rather than inside the roll, with extra pan juices spooned over the beef.

Variations

For a spicier sandwich, add more aji amarillo paste or a few slices of jalapeño. Aji amarillo is a bright, fruity Peruvian yellow chile commonly sold as a paste in Latin American markets; it is optional here, and jalapeño or red pepper flakes add heat but not the same flavor. For a milder version, omit the chile.

Swap sirloin for flank steak, or use thinly sliced strip steak. If you prefer a meat-free filling, substitute thick strips of portobello mushroom; cook until browned and tender, then season and sauce them in the same way. You can also use sweet potato fries, though their sweetness changes the balance. A soft roll works if crusty rolls are unavailable, but toast it well so it holds the juices.

Storage and Reheating

For best texture, store the beef-and-vegetable filling, fries, and rolls separately. Refrigerate the cooked filling and fries within 2 hours in covered containers; they keep for 3–4 days in the refrigerator. Store the rolls at room temperature if they will be used within a day, or freeze them for longer storage. Do not store an assembled sandwich with fries inside if you want them crisp.

Reheat only the portion you plan to eat. Warm the filling in a skillet over medium heat with a teaspoon of water, stirring until steaming throughout; leftovers should reach 165°F (74°C). Re-crisp the fries in an oven or air fryer, following the appliance’s instructions. Assemble with freshly toasted bread. Discard cooked beef or fries left at room temperature for more than 2 hours, or more than 1 hour when the temperature is above 90°F (32°C).

Frequently Asked Questions

What is lomo saltado?
Lomo saltado is a Peruvian stir-fry, commonly made with beef, onion, tomato, soy sauce, and vinegar, and often served with rice and fries. Versions vary by cook and region; this sandwich adapts its familiar flavors for a roll.

Can I make the filling ahead?
Yes. Cook the beef and vegetables, cool and refrigerate the filling within 2 hours, then use it within 3–4 days. Reheat it to 165°F (74°C) before assembling. The vegetables will soften somewhat after storage, so freshly cooked filling has the best texture.

What cut of beef works best?
Sirloin is a convenient, tender choice, while flank steak has a deeper beef flavor and benefits from being sliced thinly across the grain. Avoid very thick strips, which take longer to cook and are harder to eat in a sandwich.

Can I cook the fries in the same skillet?
It is better to cook them separately. Fries need space and dry heat to crisp, while the beef and vegetables produce sauce. If you add fries to the pan, they tend to soften; serve them alongside or tuck them into the sandwich at the last moment.

How do I keep the beef tender?
Cut it across the grain, pat it dry, and sear it quickly in a hot pan without overcrowding. Let the beef rest for 3 minutes after cooking to the safe minimum temperature, then return it briefly to the sauce so it does not overcook.

Is aji amarillo essential?
No. It contributes fruity chile flavor as well as heat, but the sandwich is still satisfying without it. Jalapeño or red pepper flakes can provide heat; neither is an exact flavor match.

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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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