If using the tofu, first marinate it. Place the tofu cubes in a shallow dish and then pour the tamari and vinegar over the pieces. Flip the tofu to try and coat and distribute the marinade to both sides of the tofu.
Next, combine the ingredients for the sauce, pureeing in a blender or with a handblender until fully blended.
In a large non-stick skillet over high heat, saute the tofu for 7-9 minutes, turning the sides to lightly brown each side. Once golden brown, remove the tofu from your skillet. (Alternatively, you can bake the tofu with the marinade in a shallow baking dish (roughly 8” x 12”) at about 400 degrees for 15-25 minutes, turning once or twice until all the marinade is absorbed - it won’t get as crispy through oven baking).
Next, in a non-stick pan over high heat, add 2-3 teaspoons of the water, and the carrot and salt. Reduce heat to medium-high, cover, and let the carrot steam for a couple of minutes. Remove cover, return heat to high, and add the zucchini. Toss through to let sear slightly, then add remaining 2-3 teaspoons of water, the broccoli, and bell pepper. Toss through, cover, reduce heat slightly, and cook for 2-3 minutes, just until broccoli turns bright green (the veggies will continue to cook in sauce, so don't overcook).
Add the teriyaki sauce to the veggie mixture, and tofu if using. Toss to coat, and let the sauce come to a slow boil over medium-high heat. Once the sauce has reached a slow boil and thickened, add the cashews and toss to combine. Remove the pan from the heat and serve immediately over brown rice, quinoa, or soba noodles.