1 1/2 pounds sirloin tips, trimmed, cut into 3-inch pieces and sliced against the grain into 1/2-inch strips
1 1/2 teaspoons ground cumin
Kosher salt and ground black pepper
5 tablespoons soy sauce, divided
3 tablespoons grapeseed or other neutral oil, divided
1 large red onion, halved and cut into ½-inch half rings
1/4 cup red wine vinegar
2 medium garlic cloves, minced
1 jalapeño chili, stemmed and sliced into thin rounds
1 1/2 cups grape tomatoes, halved
In a medium bowl, combine the steak, cumin, 1 teaspoon each salt and pepper, and 2 tablespoons of the soy sauce. Marinate at room temperature for 10 minutes. Pat the meat dry and transfer to a plate.
In a 12-inch skillet over high, heat 1 tablespoon of the oil until smoking. Add half of the meat in a single layer and cook, turning once, until well browned on both sides, 2 to 3 minutes total. Transfer to a plate. Repeat with 1 tablespoon of the remaining oil and the remaining meat.
In the same pan over medium-high, heat the remaining 1 tablespoon oil until shimmering. Add the onion and cook until just starting to soften, stirring, for 2 minutes. Stir in the vinegar and remaining soy sauce, scraping the bottom of the pan to remove any browned bits.
Cook for 1 minute until the sauce thickens slightly. Stir in the garlic and jalapeño and cook until the garlic is fragrant, about 30 seconds. Add the tomatoes, the meat and any accumulated juices to the pan. Cook until the meat is just warmed through, 30 seconds. Taste and season with salt and pepper.
Tip: Don’t cook the beef without patting it dry. Marinating in soy sauce adds flavor, but also moisture. Drying the beef helps ensure that the slices sear nicely, rather than steam. Also, cook in two batches; crowding the pan inhibits browning.