Purée dressing ingredients in a blender until smooth, about 2 minutes.
Cook pasta in a 6-to-8 quart pot of boiling salted water until tender. Drain in a colander. (Or cook Asian noodles as directed.)
Place in large serving bowl. Pour as much peanut dressing, as desired, over noodles and toss well.
Add scallions, bell peppers, and sesame seeds to noodles, toss again to combine, and serve immediately.
*Type of peanut butter for dressing - (preferably natural peanut butter, not sweetened, with natural oil that floats on top well incorporated).
**Can substitute spaghetti or an equivalent amount of rice sticks or cellophane noodles
Makes a great, quick meal from the pantry. Dressing can be thinned with warm water, if desired. Excellent served with grilled shrimp on top. If any sauce is left over, makes a great dipping sauce for sate pork or chicken or sauce for a pad Thai style stir-fry.