Add the cauliflower florets to a bowl and add the olive oil, mustard, za'atar seasoning, and salt and pepper. Mix well.
Arrange the cauliflower florets on the baking sheet and bake for 20-25 minutes, or until cooked to your preference.
Make the sauce: While the cauliflower bakes, make the tahini dipping sauce. In a small mixing bowl, add all of the dip ingredients except the water. Whisk well. Taste and add more of any flavor you prefer.
Add water slowly, until you reach a consistency you like. It'll thicken before it starts to thin out.
Serve the cauliflower with sauce on the sauce for dipping, or drizzle on top.
Video
Notes
Store leftover cauliflower in a sealed container in the fridge for 3-4 days. The tahini sauce will last about a week in the fridge.