Place a large casserole pan or skillet on medium-high heat and add oil. Add cumin seeds, coriander seeds and mustard seeds and heat until they sizzle. Then add finely sliced brown onion and cook until they start to caramelise.
Add garlic, then ginger and stir into the onion mixture. Follow with turmeric, red chilli flakes, ground coriander and stir until evenly distributed into the mixture.
Add tomato purée and stir into the mixture. Then add sliced red peppers and red onion and stir until softened. Add saffron water, lemon juice and garam masala and stir. Bring to a boil and then turn heat down to allow the sauce to simmer gently for 30 mins.
Add prawns to the sauce and stir. Add chopped fresh coriander and cook for a further 10 mins. Turn the heat off and serve the Meygoo Dopiyazeh with fresh chopped coriander sprinkled on top accompanied with rice and / or naan.