Place the flank steak in the freezer while you prepare the sauce, about 5 minutes. Whisk the soy sauce, honey, cornstarch, vinegar, onion powder, garlic powder, and ground ginger together in a small bowl until no lumps remain; set aside.
Remove the steak from the freezer. Cut the steak in half lengthwise, then slice across the grain into very thin (about 1/4-inch thick) slices.
Heat the oil in a large skillet over medium-high heat until shimmering. Season the beef with the salt and pepper. Add to the skillet, spread into an even layer, and cook undisturbed until the bottom sears, about 2 minutes. Toss and cook until the beef is cooked through, about 3 minutes more. Transfer the beef to a plate and set aside.
Add the bell peppers to the skillet and cook until tender and beginning to brown, about 3 minutes. Return the beef and any accumulated juices to the pan. Add the soy sauce mixture and cook until the sauce thickens, 1 to 2 minutes. Serve over cooked rice topped with the scallions.