Heat a wok or large skillet over medium-high heat. Spray with vegetable cooking spray. Brown tofu on both sides, then remove from pan and set aside.
Add onion to wok and sauté for 1 minute. Add broccoli, carrots, peas and red pepper; stir-fry until tender-crisp, about 5 minutes. Return tofu to wok and stir in broth, chili sauce and orange zest. Heat until bubbling.
Transfer stir-fry to serving platter and sprinkle with cilantro.