Heat 1.5 tbsp. oil in a pan and saute lady's fingers for a minute over medium heat. Lower heat, cover pan, and cook until lady fingers are tender. Set aside.
In a separate pan, heat 1/2 tbsp. oil and add the raw mango strips. Sprinkle with sugar and saute on high heat. Set aside.
In another pan, heat 1 tbsp. oil. Saute fennel and nigella seeds until they crackle. Add onion and cook until translucent. Add ginger, green chilli, salt and the spice powders. Add the sauteed lady's fingers and mango strips.
Add lemon juice and adjust seasoning. Sprinkle over with pepper powder and serve hot.