Boil a large pot of salted water and cook the spaghetti according to package instructions until al dente, about 8 to 10 minutes.

Drain the spaghetti and rinse it under cold water to cool, then spread it on a baking sheet.

Chop the cherry tomatoes, cucumber, bell peppers, and red onion. If using, slice the black olives.

In a mixing bowl, combine the cooled spaghetti with the vegetables and olives. Toss to mix.

Pour the Italian dressing over the salad and toss well to coat all ingredients.

Season with salt and black pepper to taste, adding Parmesan cheese if desired.

Cover and refrigerate for at least one hour before serving.