Bring 4 quarts water to a boil in a large pot over high heat. Add the pasta and cook, stirring occasionally, until al dente, about 12 minutes. Drain completely (do not rinse) and place in a large bowl.
While the pasta is cooking, halve the cherry tomatoes lengthwise. Cut the bell pepper in half, discard the seeds, and cut into ½-inch dice. Peel the cucumber and cut in half lengthwise, remove the seeds, and slice into half-moons. Halve the olives lengthwise.
In a small bowl, combine the yogurt, mayonnaise, lemon zest, onion powder, salt, and pepper. Add the yogurt mixture and the vegetables to the pasta and toss to evenly coat.