Cook the Penne pasta until al dente. Drain and rinse in cold water. Lightly coat the pasta with olive oil to prevent the noodles from sticking together.
While the pasta cooks, slice the cucumbers and onion. Once cooled, put the pasta in a large bowl and add sliced vegetables.
In a small bowl, whisk together the remaining ingredients. Pour over salad and stir to coat. Cover and chill for 4 hours. Refrigerate leftovers.