In a small saucepan combine the peanut butter, soy sauce, vinegar, lime juice, garlic, cayenne and hot water. Whisk the sauce together over moderate heat until smooth and hot.
In a kettle of boiling salted water cook the pasta for 5 minutes. Add the sliced carrots to the cooking pasta, stir and cook for 1 minute. Add the broccoli, stir and cook for 30 seconds. Add the snow peas, stir and cook for another 30 seconds. Drain the pasta and vegetables in a colander.
Transfer the pasta and vegetables to a large bowl and pour the hot sauce over the mixture, tossing to combine. Sprinkle with scallions.
Recipe courtesy of Gourmet Magazine