Preheat your oven (or air fryer) to 400° F. Spread your tofu batons onto a baking sheet lined with parchment paper. Once your often is preheated, place the baking sheet in the center rack and bake until the corners begin to turn golden brown, around 20 minutes (will be more like 10 minutes in the air-fryer).
In the meantime, boil your spinach by adding them to a large pot of boiling water. Cook until they turn bright green, about 1 minute. Then drain and run under cold water, to stop the cooking process. Squeeze out any excess liquid and place your spinach aside.
Stir-fry all the vegetables by adding vegetable broth to a large non-stick wok or skillet over medium high heat. When the broth starts to bubble (about 1 minute), add shiitake mushrooms, all the bell peppers, red onion, scallion, green and purple cabbage, carrot, and garlic. Cook until they just start to soften, about 4 to 5 minutes. Turn off the heat but keep the veggies in the pan.
Cook your noodles by adding them to boiling water for about 7 minutes. The noodles should be chewy, not hard. Reserve about 1 cup of the cooking water. Then, drain the noodles and run them under cold water. Add these to the pan of stir-fried vegetables.
Add the baked tofu and spinach to the pan of noodles and veggies. Then, add low-sodium soy sauce, rice vinegar, maple syrup, sesame seeds, black pepper, and a tablespoon or two of the noodle cooking water. Turn the heat onto very low and stir vigorously until all the ingredients are well combined (about 1 to 2 minutes). If your noodles seem dry, add a little more of the cooking liquid. Remove from heat and serve.