Place 3 cups of water, turmeric, cinnamon, cardamom and salt in a large saucepan. Bring to the boil and add rice. Cook according to the instructions on the packet. Once cooked, strain and keep warm.
Heat oil in saucepan over medium heat and fry the cumin and mustard seeds until they splutter. Add the tomato and stir until coated with the seeds, then stir in the ground spices, sugar and 1 tsp salt. Add vinegar and then reduce heat and simmer for a few minutes. Allow to cool slightly and sprinkle with coriander, ready to serve.
Get your curry boiling, add prawns, cook quickly for 2-3 minutes until just cooked through. Serve with rice, tomatoes, lime and raita.
Recipe by Eatin' mess at https://eatinmess.com.au/recipes/prawn-curry-sweet-sour-tomatoes/