Preheat the oven to 180 C. Toss the Paneer in the Za'atar. Assemble the kebab sticks, starting with the Paneer, then onion, Paneer, onion. Repeat for all four sticks. Place kebabs on baking tray, sprinkle on the zest and squeeze on the lemon juice. Season with the salt, then place in oven for 20 mins, until Paneer starts to brown.