Wash the eggplants, cut off the stem end if using large ones and cut in half lengthwise. With the tip of a sharp knife, make at least 3 lengthwise slashes on the cut sides of the eggplants, being careful not to pierce the skin on the opposite side. Sprinkle with salt and let stand for 30 minutes. Rinse with cold water, dry, and invert to drain. Meanwhile, put the onions in a small pan with the 1/2 cup water and simmer a few minutes. Drain and discard the water or save for soup. In a medium frying pan, heat 2 tablespoons of the oil and saute the onions until soft, then put approximately a third of them in the bottom of a buttered casserole large enough to accomodate all the eggplants. Set 4 to 5 tomato slices over the onions in the casserole and add the rest of the tomatoes to the onion remaining in the frying pan. Saute onions and tomatoes for 10 minutes, then stir in all but 2 tablespoons of the parsley and remove from the heat. Set the eggplants into the casserole, tuck a slice of garlic into each eggplant slash, and stuff the slashes with the filling, allowing some to cover the top of the eggplant. Season lightly with salt, pepper, and a pinch of sugar, then dribble the remaining oil and chopped parsley over the eggplants. Cover the casserole with a lid or aluminum foil and bake in a moderate oven 350F for 30 to 40 minutes, until fork-tender, removing the cover during the last 10 minutes, to allow the sauce to thicken. Garnish with parsley and serve warm. Note: This is excellent as a first course of a subsequently light meal topped with fresh fruit and Turkish coffee. If you wish, you may leave the eggplants whole, slash one side and remove some of the pulp with a small spoon. This pulp is then sauteed with the filing and stuffed into the eggplant, a very attractive method for the smaller eggplants. As you might suspect, both variations may also be prepared on top of the stove.