Make sure the okra is completely dry before cutting — any moisture makes it slimy. Cut into 1-inch pieces.
Heat 2 tablespoons of oil in a wide pan over high heat. Add the okra in a single layer and sauté for 6–7 minutes, stirring occasionally, until lightly browned. Remove and set aside.
In the same pan, heat the remaining oil. Add cumin seeds and let them crackle.
Add the sliced onion and sauté on medium-high heat for 5 minutes until golden.
Add ginger-garlic paste and cook for 1 minute. Add tomatoes, turmeric, red chilli powder and coriander powder; cook until the masala thickens and oil separates, about 6 minutes.
Return the fried okra to the pan. Add salt and amchur, and toss gently to coat.
Cook uncovered for 4–5 minutes on medium heat so the flavours combine.
Garnish with coriander leaves and serve hot.