1. Make dressing: In a bowl, whisk together vinegar, buttermilk, lemon juice, oil, garlic, mustard, parsley and dill. Season with salt and pepper.
2. Bring a large pot of salted water to a boil. Cook macaroni for about 10 minutes, or as package label directs. Stir in peas 2 minutes before end of cooking time. Drain; rinse under cold water until cool. In a large bowl, toss macaroni, vegetables and dressing.