Press your block of tofu very well. Mix the za’atar with the oil and rub it into the tofu. Place it into a glass pyrex dish and place into the refrigerator to marinate for at least two hours or overnight.
Preheat your oven to 375. Slice off the top of a whole head of garlic and place into a small glass pyrex dish. Drizzle with the 2 tablespoons of olive oil, then cover the dish with aluminum foil. Roast for about 30 minutes, then flip the entire head over, spooning the olive oil over the top. Then roast for 15 minutes more, uncovered. Let it cool completely before separating the bulbs from the papery skins.
Heat a little oil in a small cast iron pan over medium-low heat. Place the sliced onion into the pan and allow it to soften and slightly brown for about 20 minutes, stirring occasionally. Add in the mushrooms and let cook for about 10 minutes.
While your vegetables are cooking, heat up another skillet over medium heat. Place the tofu into the pan and cook for a few minutes on each side. (Grilling or baking should work well, too.)
Return to your cast iron skillet. Toss in the tomatoes and soften for just a few minutes.
Make your tahini sauce by whisking together the tahini, water and apple cider vinegar. Set aside.
Toss your tofu, garlic and vegetables together. Drizzle any leftover za’atar/oil mixture over the top. Serve with the fresh chopped parsley, cracked pepper and tahini.