Preheat the oven to 375°F. Grease a 12-cup Bundt or tube pan., To make the bread: Divide and roll the dough into 24 golf ball-sized pieces. Dip them in the melted butter and roll in the za'atar to coat evenly, then pile them into the prepared pan. Cover and let rise for 30 minutes., Uncover the bread and bake it for 30 to 40 minutes, until its internal temperature reaches 190°F. Begin checking for doneness at 30 minutes. Let cool for 20 minutes in the pan on a rack, then tilt the bread out of the pan onto the rack to cool a bit more before serving., To make the labneh: In a medium bowl, combine the labneh, garlic, onion, sumac, and a sprinkling of salt and pepper. Drizzle with olive oil and serve with the monkey bread., Store any bread leftovers at room temperature, well wrapped, for several days. Freeze for longer storage. Refrigerate labneh in an airtight container for up to a week.