Cook the pasta in well-salted boiling water until just al dente. Drain and rinse under cold water to stop cooking and cool quickly. Drain thoroughly.

Whisk together mayonnaise, sour cream, red wine vinegar, olive oil, Dijon mustard, Italian seasoning, garlic powder, salt, and pepper in a bowl. Taste and adjust acidity or salt.

In a large bowl, combine cooled pasta, tomatoes, cucumber, bell pepper, onion, olives, and cheese (if using).

Pour dressing over the pasta mixture and toss gently to coat everything evenly.

Fold in chopped parsley and grated Parmesan. Cover and chill at least 1 hour — overnight is best for flavor.

Before serving, toss again and adjust seasoning as needed.