Meanwhile, place the peanut butter and water in a large bowl and whisk until smooth. Add the soy sauce, gingerroot, rice syrup, rice vinegar, chili powder and cayenne pepper and whisk.

When the spaghetti is done, rinse it with cold water and drain. Add the spaghetti and onions to the peanut sauce and toss well until the spaghetti is coated with the sauce. Refrigerate for several hours or overnight.

Before serving, toss the spaghetti again. Divide among four plates and sprinkle raisins over each serving.