1 To make the dressing, in a small bowl, place the yogurt, vinegar, olives, thyme and garlic. Stir to combine, then season with salt and pepper to taste. Set aside.2 Cook the pasta in boiling salted water according to package directions. Drain in a colandar, then rinse well and drain again.3 Drain tuna and place in a large bowl with the walnuts and peppers and toss to combine.4 Before serving, add the dressing and stir to coat the ingredients evenly.5 Sprinkle with parsley.