In a mixing bowl take 1/2 cup of besan or gram flour.
Add a big pinch of salt and mix it. Now add little water and make a thick paste. Keep the mixture aside.
Now take a wok or karahi and heat it at medium heat. Add 2 tbsp of oil and let it heat.
Stir in 1 tsp of cumin seeds and let them crackle. Add 2 fine chopped green chillies.
To this add 1/2 cup of fine chopped onions. Mix well and cook onions for 5 minutes. Now add 1 tsp of ginger garlic paste, salt and mix it well.
Saute and cook onions and let them turn light brown. Now add 1/4 tsp of turmeric powder, 1/2 tsp of red chilli powder, 1 tsp of coriander powder and 1/4 tsp of garam masala.
Mix everything well and add 2 fine chopped tomatoes and mix them. Add 1-2 tbsp of water to avoid burning. Mush the tomatoes little bit with spatula to make them paste.
Now put the stove heat to lowest. Now pour gram flour mixture on top of onion tomatoes. Cover and let it cook for 5 minutes.
After 5 minutes open the lid and mix the besan well. Continuously stir and cook besan and let it get nicely roasted.Add 1/2 tsp of dry mango powder and 2-3 tbsp of fine chopped coriander leaves.