In bowl, whisk together soy sauce, vinegar, canola oil, lime juice, honey and onion powder. Incorporate tofu and marinate for 15 minutes (reserve marinade).
In wok, heat canola oil over medium-high heat. Cook tofu for about 2 minutes per side or until golden. Set tofu aside.
In same wok, stirring constantly, cook onions for 3 – 5 minutes or until browned. Add bell pepper, bok choy stems, ginger and garlic; cook for 3 minutes. Add mushrooms; cook for 2 minutes. Add bok choy greens, reserved marinade and tofu; cook for 2 minutes. Serve immediately.