In a shallow dish, add tofu. Pour soy sauce and vinegar over tofu and marinate for 10 minutes or longer. I marinated for about 30 minutes. (Flip tofu at least once while marinating).

While tofu marinating in a large bowl, whisk all ingredients for teriyaki sauce until arrowroot powder is dissolved (or put it in a blender to puree). Heat the sauce and until the mixture get thickened little bit.

In a large frying pan or wok on high, heat 1 tablespoon oil. Add tofu and sauté for 4-5 minutes, and then turn over to sauté for another 3-4 minutes, until lightly brown on each side. Remove from pan and set aside. Reduce heat to medium, add 1 tablespoon oil to wok, and add broccoli, carrot, bell pepper and water. Toss, cover and cook for 4-5 minutes, until broccoli turns bright green. Add teriyaki sauce and increase heat to high. Toss to coat, and let sauce come to a slow boil. As soon as sauce has reached a slow boil and has thickened, add tofu, cashews and green onions (if using), and toss to combine. Remove pan from heat and serve immediately.