Make pesto: In a food processor puree basil, parsley, garlic, lemon juice, salt, pepper and pine nuts until smooth. With motor running, add olive oil and process until a thick paste forms. Add Parmesan and pulse twice. Season with more salt and pepper, if desired.
Make salad: Cook pasta according to package directions until al dente. Drain and run under cold water to stop cooking.
In a large bowl, combine pesto and Greek yogurt and stir until well blended. Add cold pasta and toss to coat with dressing. Top with tomatoes. Serve salad at room temperature or cover and refrigerate to serve chilled.