Heat the pan into medium heat, drizzle 3 tablespoons of oil and saute the onions are 2-3 minutes until soft. Then add the garlic and stir for another 2-3 minutes until the onions are light brown.
Next, add the chopped tomatoes and cook until the tomatoes are reduced and colour changed. ( It usually takes about 3-4 minutes to soften and reduce the tomatoes. ) Then add the tomato puree and follow with the spices, turmeric, chilli powder, coriander powder, cumin powder, and salt. Stir it well for few seconds.
Pour the water in, and bring it to simmer. Then add the king prawns and cook for another 3-4 minutes and follow with the bell peppers. Cook until the prawns and peppers are cooked through.
Make a taste test and add more salt or water according to your preference.
Turn off the heat and sprinkle chopped coriander. Transfer to serving plate and serve immediately with plain rice, naan, or chapati.