Preheat the oven to 400°F with a rack in the center position. Line a sheet pan with parchment paper.
Make the cauliflower. On the prepared sheet pan, toss the cauliflower with the olive oil. Spread the cauliflower into a single layer and sprinkle with the Za’atar and salt.
Roast for 45 minutes, or until golden and tender (see Note).
Meanwhile, make the whipped feta. In the base of a food processor, combine the feta, cream cheese, garlic, dill, Za’atar, olive oil, and lemon juice. Blend until smooth, 3-4 minutes.
Transfer the cauliflower to a plate and garnish with the parsley. Serve with the whipped feta on the side.
