Cook the spaghetti in salted boiling water according to package instructions until al dente, about 8-10 minutes. Drain and rinse under cold water.

In a large bowl, combine cherry tomatoes, cucumber, red pepper, zucchini, and black olives. Add optional bell pepper and red onion, soaking onions in cold water if desired.

Add the cooked spaghetti to the vegetables. Sprinkle celery seed, paprika, and garlic powder over it. Pour the Italian dressing and add Parmesan cheese. Toss gently to combine.

Cover the bowl with plastic wrap and chill in the refrigerator for at least 1 hour to let the flavors meld.

After chilling, toss the salad again and adjust seasoning. Serve cold as a side dish or light meal.