In a large saucepan, heat 4 tbsp oil on medium heat.
Add the diced onions and sprinkle with a pinch of salt. Cook for 5-7 minutes until the onions start to turn translucent and soften.
Add 1 tbsp minced garlic and chopped green chillies, if using. Cook for 1-2 minutes until fragrant and add the diced tomatoes. Cover and cook 5 minutes until the tomatoes are softened.
If the tomato mixture is looking a bit dry, add a splash of water (about 1/4 cup) to help the tomatoes breakdown into the curry.
Add 1/4 tsp turmeric, 1/2 tsp salt, and a pinch of black pepper. Cook for 1 minute, and then add the roasted eggplant flesh.
Cook for 5 minutes to allow the eggplant to breakdown into the curry. Again, if it looks a bit too dry, add a splash of water. Taste and adjust salt and spice to your liking.
Add the chopped cilantro leaves and 1 tbsp of yogurt and cook for final 3-5 minutes.
Turn off the heat, and serve immediately with rice, naan, or even as a warm dip.