Cook the capellini according to package directions. Drain and place in a large bowl.
Place the peanut oil, soy sauce, vinegar, sesame oil, sugar, pepper flakes ginger, garlic, and salt in a food processor fitted with a steel blade and process for 30 seconds. Pour the dressing over the noodles and mix thoroughly to coat all the pasta strands. Add the radicchio, scallions, and cilantro. Mix just to blend.