Season the prawns with cinnamon, salt and black pepper. Saute the garlic and onions in the oil untill they are soft. blend in the tomato puree diluted with a little water, add this to the pan mixture add in fresh tomato puree, stirring well. Allow to simmer on a gentle heat about 10 minutes. Add the prawns and cook on a medium to high heat for about 10 minutes. stir and remove from heat when tender. sprinkle with lemon juice and coriander leaves. Serve with plain rice.