Preheat the oven to 375. Slice the eggplants in half lengthwise. Use the end of a knife to deeply score the eggplants in a 1/2 inch cube pattern without slicing through the skin. Brush with oil, sprinkle with granulated garlic, salt, and pepper to taste. Place cut side down on a baking sheet and bake until easily pierced with a thin knife, about 20-30 minutes.
Meanwhile, in a large skillet saute the onion and garlic until fragrant. Add the lamb and saute until very nearly cooked through about 10 minutes. Drain off any access fat if desired. Add the tomatoes and spices, saute, stirring occasionally until the lamb is cooked through and the liquid from the tomatoes evaporates and mixture thickens.
Remove the eggplants from the oven. Place, cut side up, on plates or a serving platter and top with lamb mixture, pressing it into the eggplant with the back of your spoon.
In a small bowl, whisk together the sauce ingredients and immediately divide among the eggplants. Sprinkle with additional za'atar if desired.