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

While the pasta is cooking, thinly slice the red onion and soak in cold water for about 10 minutes to mellow the taste. Drain well before adding to the salad.

In a medium mixing bowl, whisk together mayo, Dijon mustard, red wine vinegar, oregano, sugar, salt, and pepper. Slowly whisk in olive oil until smooth.

In a large mixing bowl, combine soaked onions, diced salami, roasted red bell peppers, pepperoncini, pickled teardrop peppers, cherry tomatoes, and mozzarella. Toss with the dressing.

Fold in the cooled pasta and chopped basil, stirring gently. Adjust seasoning with more salt and pepper if needed.

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