Bring a large pot of salted water to a rolling boil. Add short pasta and cook until al dente, about 8-10 minutes. Drain and rinse under cold water.

In a small bowl, soak thin slices of red onion in cold water for 10 minutes to mellow their flavor, then drain.

In a mixing bowl, whisk together mayonnaise, dijon mustard, and red wine vinegar until creamy. Add oregano, sugar, salt, pepper, and olive oil, mixing until smooth.

In a large bowl, combine soaked onions, salami, roasted red bell pepper, pickled peppers, pepperoncini, and cherry tomatoes. Pour in the dressing and toss to coat.

Gently fold in cooked pasta and mozzarella balls. Add fresh basil and mix until combined.

Cover and refrigerate for at least 1 hour to let the flavors meld.