To blanch the cauliflower, bring 2 quarts of water to a boil in a large pot. Add in cauliflower and bring back to a boil. After 1 minute remove florets and cool in an ice bath. Drain thoroughly and place in a non-reactive bowl.
Slice the onion and carrots thinly and place in separate non-reactive bowl.
To prepare pickle mixture, stir together remaining ingredients in a pot and bring to a boil. Then pour this hot liquid over vegetables and let sit until cool at least 1 hour.
Plate strained vegetables in colorful piles on a plate and sprinkle with fresh cilantro.
Make ahead: Vegetables can be refrigerated with brine for up to 1 week.