Preheat oven to 275 degrees. Line a heavy baking sheet with parchment paper. Slice tomatoes in half. In a bowl, combine tomatoes with olive oil, salt, and pepper. Stir gently until combined.
Place the tomatoes on the baking sheet with the cut side up. Then, sprinkle each tomato with the za’atar.
Roast the tomatoes for two hours or until they are mostly shriveled.