Tender beef tenderloin seared hard and fast with red onion, ají amarillo, and tomato in a glossy soy and vinegar sauce, served over crispy hand cut fries with white rice. This is the Peruvian classic I learned to make in Peru.
Rinse the cut potato sticks in cold water to remove excess surface starch, then dry them thoroughly with paper towels.
Heat 1 inch of oil in a heavy-bottomed pot or Dutch oven to 325°F (165°C). Fry the potatoes slowly for 25 to 30 minutes, stirring occasionally, until deeply golden, blistered, and crisp throughout. Drain on a wire rack, then place in a bowl and toss immediately with salt. Keep warm.
For the Beef Stir Fry
In a bowl, toss the sliced beef tenderloin with the ½ teaspoon kosher salt and the black pepper until evenly coated.
Heat a large wok or heavy skillet over high heat until smoking hot. Add 2 tablespoons of the oil. Add half the beef in a single layer and sear undisturbed for 1 to 2 minutes, until a dark char develops. Flip and cook 1 minute more, then transfer to a plate.
Add 1 tablespoon of the oil and sear the second batch of beef the same way. Set aside on the plate.
Add the remaining 1 tablespoon of oil to the hot pan. Add the red onion, ají amarillo, and garlic. Stir fry over high heat for 1 to 2 minutes, until the garlic is fragrant and the onions are lightly charred at the edges but still crisp.
Return the beef and any resting juices to the pan. Add the tomato wedges and green onions. Pour the red wine vinegar and soy sauce around the perimeter of the pan. Toss continuously over high heat for 45 to 60 seconds, until the sauce reduces into a glossy glaze that coats the meat and vegetables.
Remove from the heat and fold in the chopped cilantro. Arrange the crispy fried potatoes on a serving platter or individual plates, spoon the beef and vegetables over the top, and serve immediately with warm white rice.
Notes
Storage: Refrigerate the beef and vegetables in an airtight container up to 3 days, storing the fries separately. Reheat the beef in a hot skillet and re-crisp the fries in a 400°F (204°C) oven or air fryer. Not recommended for freezing.