Combine the peanut butter, tahini, soy sauce, sesame oil, sriracha, rice vinegar, brown sugar, ginger and ¼ cup water in small saucepan. Heat over low heat and stir just to combine. Turn off heat and reserve.
Use a vegetable peeler to peel the carrots into thin “ribbons” and reserve.
Bring a large pot of salted water to a boil. Cook the broccoli until bright green and crisp (about 1 minute). Add the carrots and cook another 30 seconds.
Remove broccoli and carrots (do not drain) and run under cold water to stop the cooking. Use the same water to cook the noodles to al dente, according to package directions. Drain and run under cold water to stop the cooking.
Toss the noodles with the broccoli, carrots, red pepper, tofu and reserved sauce. Arrange on a platter and sprinkle with scallions.
Note: This dish can be made gluten-free by using gluten-free buckwheat soba noodles and ensuring the condiments contain no gluten.