Mix together brown sugar, soy sauce, lime juice, sriracha, hoisin sauce, and water. Set aside.
Bring a large pot of water to a boil. When the water reaches a boil, add rice noodles and cook until al dente, about 5 minutes. Drain, rinse under cold water and set aside.
Toss the tofu cubes and cornstarch in a medium bowl until well-coated. In a large skillet or wok, heat 1 tablespoon oil over medium-high heat. Add tofu and stir-fry for 5 to 7 minutes, or until the tofu is lightly golden brown on all sides. Remove from the pan with a slotted spoon and set aside.
In the same pan over medium-high heat, add red onion, the whites of the scallions and shredded cabbage and stir-fry for 2 to 3 minutes or until the onion starts to char slightly and the cabbage has wilted.
Add in blanched noodles and fried tofu and cook for 1 to 2 minutes.
Push the noodles to one side of the pan and add eggs to the empty space. Cook the eggs until lightly scrambled, then stir to combine with the noodles.
Add sauce to pan and stir fry until the noodles absorb most of the liquid, about 2 minutes.
Serve topped with lime wedges, crushed peanuts, and green scallion tops.