Grind all ingredients in a blender or in a mortar and pestle (excluding tomatoes, onions and use only half the amount of vinegar at this stage) until it forms a thick paste.
In a large bowl mix roo with the paste, cover and set aside for 15-20 minutes.
Heat oil in a pan, fry onions for 2-3 minutes, add meat and fry until browned, then followed by adding tomatoes, stirring until tomatoes are completely broken up.
Keep frying on low heat until the oil separates from meat (oil will come to the top).
Add remaining vinegar, cover and simmer for 40-50 minutes, until meat is tender.
Water may be added if necessary, although sauce should be fairly thick.
Serve with rice and garnish with coriander.