In a small bowl, combine all sauce ingredients and mix well until the brown sugar and cornstarch are dissolved.
Blot sliced tofu thoroughly with paper towels to remove excess liquid. Place the sesame seeds in a small bowl and press each slice of tofu into the seeds on both sides to coat.
In a large pot, bring water to a boil so that soba noodles can be cooked immediately before serving.
In a large non-stick skillet, heat 1 tbsp of the sesame oil over medium high heat. Sauté the tofu on both sides until tofu is heated through and sesame seeds are lightly browned about 3 minutes on each side). Remove tofu from pan and set aside.
Heat another tbsp of sesame oil in the same skillet. Add the zucchini noodles and sauté for about 5 minutes or until tender. Remove from skillet and set aside.
Add soba noodles to the cooking water and cook according to package. While noodles cook, add the sauce mixture to the same skillet and stir over low heat for 1 minute or so or until slightly thickened.
Assemble bowls with both types of noodles and tofu, top with sauce and serve immediately.