Heat oil in a nonstick or heavy bottomed skillet over high heat. Add the onions, and sauté until they are lightly golden (~8-10 minutes).
Lower the heat to medium and add the garlic, ginger and cumin seeds. Sauté until the raw smell of the ginger and garlic disappears (~1 min). Add the tomato, salt, coriander powder, black pepper powder, and red chili powder. Sauté for a minute, then stir in the zucchini and 1/4 cup of water. Mix well, ensuring that the zucchini is well coated.
Cover and let cook on medium heat for 7-10 minutes, stirring once in between. Once most of the water has dried up, use a wooden spoon to break the zucchini into pieces. Add the sliced green chili pepper and turmeric and sauté for a few minutes.
Lower the heat to the lowest setting, cover and continue to cook for 15-20 minutes, stirring half-way. If you’re afraid it will stick to the pan, add a splash of water. Uncover and stir well. If needed, raise the heat to high to sauté any extra moisture for 3-5 minutes. Taste and adjust salt.
When the water has completely dried up and the zucchini is very well cooked, turn off the heat and garnish with cilantro, if desired. It is typically eaten with roti or naan but you can serve it with any type of bread or rice.