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

Wash and chop vegetables: halve the cherry tomatoes, dice the cucumber, green and red bell peppers, finely chop the red onion and slice black olives if using.

In a large mixing bowl, combine the cooled spaghetti with the prepared vegetables. Gently toss to mix evenly.

Drizzle the Italian dressing over the pasta and vegetable mixture. Toss carefully until everything is well coated.

Season to taste with salt and pepper. If desired, add grated Parmesan on top.

Cover the salad and let it chill in the refrigerator for at least one hour to enhance flavors.