Bring a large pot of salted water to a rolling boil, then add cauliflower florets. Blanch for 1-2 minutes until bright white and slightly tender. Transfer florets to an ice bath to stop cooking.

After cooling for about 5 minutes, drain the cauliflower florets and pat them dry with a clean towel.

In a large mixing bowl, combine blanched cauliflower, halved cherry tomatoes, thinly sliced red onions, black olives, green olives, and parsley. Toss gently.

In a separate bowl, whisk together olive oil, red wine vinegar, Dijon mustard, minced garlic, oregano, and basil. Season with salt and black pepper.

Drizzle the dressing over the mixed vegetables and toss gently to coat all ingredients.

Cover the salad and refrigerate for at least 30 minutes to allow flavors to meld.

Once marinated, give the salad a final toss, adjust seasoning if needed, and serve.