Cook Pasta In A Large Pot Of Boiling Water Until Done. Drain. Meanwhile, Combine Oil And Onions In A Small Skillet. Saute Over Low Heat Until Tender. Add Ginger; Cook And Stir For 1 To 2 Minutes. Mix In Peanut Butter, Soy Sauce, Water, Vinegar, Sugar, And Red Pepper Flakes. Remove From Heat. Toss Noodles With Sauce, And Serve.