Blanch the cauliflower florets in salted boiling water for 2 minutes, then drain and rinse under cold water immediately.
Dry the florets thoroughly by spreading them on a clean towel. Pat dry if needed before marinating.
Whisk together olive oil, lemon juice, garlic, oregano, cumin, red pepper flakes, salt, and pepper in a large bowl.
Add the dry cauliflower to the marinade and toss well to coat. Cover and refrigerate for at least 30 minutes, ideally 1 hour.
Fold in cherry tomatoes, olives, red onion, and parsley. Toss gently and adjust seasoning to taste.
Top with crumbled feta right before serving if using. Serve cold or at room temperature.
