Chop the green onions, the white parts, 1/4 inch long and the green parts 3/4 inch long. Set aside.
In a large mixing bowl, combine yogurt, chili powder, turmeric, cayenne and salt. Add eggplant, tomatoes and onions and stir well to make sure the veggies are well coated.
In a shallow heavy pan, heat oil on medium-high heat for 45 seconds. Pour curry into the pan and stir well.
Sauté about 3 minutes, reduce the heat to medium-low and cover. Simmer for another 10 minutes, stirring once halfway. Turn off the heat and stir once more.
If you are not serving the curry right away, remove the lid or it will become to mushy.