With the rack in the middle position, preheat the oven to 425°F (220°C).
On a non-stick or parchment paper-lined baking sheet, toss the onions with the oil and curry powder. Season with salt and pepper. Bake for 15 minutes or until the onions start to brown.
Meanwhile, in a pot of salted boiling water, cook the noodles until tender, about 4 minutes. Drain.
Add the noodles, soy sauce and red pepper flakes to the cooked onions. Mix well. Bake for another 5 minutes.
Remove from the oven and add the chicken, red onion, radishes, cilantro and marinated ginger, if desired.