Chop the cauliflower into florets, then spread the florets onto a baking sheet in a single layer. Drizzle the florets with the olive or avocado oil, then toss the cauliflower with your (clean) hands to coat in the oil. Roast for 25-30 minutes, or until the cauliflower is soft, caramelizing in spots, and can be easily pierced with the tip of a sharp knife.
Add the smashed garlic and lemon juice to the bowl of a food processor. Pulse a few times until the garlic is minced.
Add the roasted cauliflower to the food processor, along with the tahini, salt, and cumin. Pulse several times to break up the florets. Flip the motor to continuous. With the motor running, pour 4 tbsp extra virgin olive oil through the feed tube. Continue processing until the hummus is smooth, stopping one or two times to scrape down the sides of the bowl.
Scrape the hummus into a bowl and drizzle with the remaining 2 tbsp extra virgin olive oil. Dust with the zaatar, and serve immediately with sliced vegetables or grain free seed bread. Store leftovers in a lidded container in the fridge for up to three days.