Instructions

1. Cut 1 1/2 pounds flank steak across the grain into rough 3x1/2 inch strips and place in a medium bowl. Add 1 1/2 teaspoons ground cumin, 1 teaspoon kosher salt, and 1 teaspoon ground black pepper, and toss to coat. Let sit at room temperature for 10 minutes.
2. Meanwhile, prepare the following: Halve and cut 1 large red onion into 1/2-inch thick slices. Stem 1 fresh or frozen ají amarillo chili pepper and slice crosswise into thin rounds. Mince 2 garlic cloves. Core and cut 2 medium plum tomatoes into 8 wedges. Finely chop the leaves and tender stems from 1/4 bunch fresh cilantro until you have 1 tablespoon.
3. Heat 2 tablespoons of the neutral oil in a wok or 12-inch cast-iron skillet over high heat until smoking. Add half the beef and spread into a single layer. Cook until browned, about 30 seconds per side. Transfer to a plate. Repeat cooking the remaining beef and adding to the plate.
4. Add the remaining 1 tablespoon neutral oil to the pan. Add the onion and cook just until crisp-tender, about 1 minute. Transfer to the plate with the beef.
5. Add tomatoes to the pan and sear one side until blistered, about 30 seconds. Add the garlic and ají amarillo and cook until fragrant, about 30 seconds. Add 1/4 cup red wine vinegar and 3 tablespoons soy sauce, scraping up the browned bits from the bottom of the pan with a wooden spoon. Return the beef, onion, and the accumulated juices on the plate to the pan and cook until the sauce thickens slightly, about 1 minute.
6. Divide 2 cups cooked long-grain white rice and 2 cups French fries between 4 plates. Spoon the lomo saltado onto the plates with the pan juices, then garnish with the cilantro.