Bring a large pot of water to a boil. Once boiling, add the cauliflower florets and sliced carrots and boil for 15-20 minutes, or until tender. Drain and let it cool for 10-15 minutes.
Transfer to a high-speed blender. Add the water, nutritional yeast, onion powder, apple cider vinegar, sriracha, vegan butter, coconut sugar, salt, garlic, and fermented tofu if using. Blend until smooth. Taste and adjust saltiness and spiciness to your liking.
Bring a medium saucepan of salted water to a boil. Once boiling, add the macaroni and cook until tender, according to the package instructions. Drain the macaroni and add them back to the saucepan. Pour in the sriracha sauce and stir to coat. Heat over medium heat for 3-5 minutes, just to reheat the sauce.
Serve warm with a drizzle of the tahini sauce and chopped green onions!
Whisk together all the ingredients in a small bowl until fully combined.