Bring large pot of salted water to a boil. Cook spaghettini according to package directions until al dente. Drain and set aside.
While pasta is cooking, spray a large skillet with nonstick cooking spray and preheat over medium heat. Saute cabbage, red pepper and carrot for 3-5 minutes. You want the carrots and cabbage to soften while keeping some texture in the red peppers. Add in garlic and cook until fragrant. (You don't really want color on the veggies, just trying to soften. Feel free to reduce temperature down to medium low or low.)
While veggies are cooking, in a liquid measuring cup or bowl, whisk broth together with cornstarch, soy sauce, peanut butter powder, truvia, ginger and red pepper flakes.
Pour peanut sauce over veggies and bring to a simmer. Sauce will thicken once bubbling. Once thick, toss with cooked pasta.
Top with chopped green onions and peanuts and serve warm (or cold.)
For a protein boost, add rotisserie or pre-cooked chicken to the finished noodles.