Bring a large pot of salted water to a rolling boil. Add the pasta and cook according to package directions until al dente. While the pasta cooks, proceed with preparing the other ingredients.

Once cooked, drain the pasta thoroughly using a colander. Rinse with cold water to stop the cooking process and cool the pasta down; this also helps prevent sticking. Drain very well again and set aside.

While the pasta is cooking, prepare the vegetables and cheese. Halve the cherry or grape tomatoes, thinly slice or finely dice the red onion, pit and halve the Kalamata olives, and crumble the feta cheese. Chop the fresh basil.

In a small bowl, whisk together the basil pesto, extra virgin olive oil, red wine vinegar, Dijon mustard, and freshly ground black pepper until well combined. Taste and add salt if needed, keeping in mind that pesto and feta can be quite salty.

In a large mixing bowl, combine the cooled, drained pasta, halved tomatoes, sliced red onion, halved Kalamata olives, crumbled feta cheese, and chopped fresh basil.

Pour the pesto dressing over the pasta and vegetable mixture. Toss gently but thoroughly until all ingredients are evenly coated with the dressing.

Cover the bowl and refrigerate for at least 30 minutes (or preferably 1-2 hours) to allow the flavors to meld and for the salad to chill completely. Toss again just before serving.