To make the Tofu Teriyaki, combine all ingredients except tofu in shallow container. Add tofu, and toss to coat. Set aside to marinate for 10 to 15 minutes, stirring once or twice.
Meanwhile, bring the rice and 3 cups water to a boil in saucepan. Cover, reduce heat to medium-low, and simmer for 30 minutes, or until all water is absorbed. (For a more tender grain, add ½ cup water and cook until absorbed.)
Remove the rice from the heat and stir in the vinegar, sugar, and salt. Stir in the nori and set aside.
Heat large non-stick skillet over medium-high heat. Add the tofu and marinade, and cook 5 to 7 minutes, turning gently, until tofu cubes are browned and crisp on most sides.
To serve, divide the Sushi Rice among six serving bowls.
Top with Tofu Teriyaki, avocado, carrots, and cucumber. Garnish with extra nori, sesame seeds, and optional scallions.