Preheat the oven to 425 degrees F.
Toss cauliflower with cornstarch, olive oil, and sea salt. Arrange on a baking sheet, making sure not to overcrowd and roast for 20 minutes.
Meanwhile, mix together mayo, rub and vinegar to make an aioli.
After removing cauliflower from the oven, while still hot, toss with aioli and transfer to a serving dish. Top with green onions, cashews, and habanero slices.