1. Wash and wipe the tomatoes. Cut into fours and leave in a large-mouthed vessel.
2. Grind the chillies, ginger and garlic to a fine paste in half the vinegar. Add this ground masala to the tomatoes and cook until the tomatoes turn soft and the masala are done. Remove from fire, cool and strain to take out the thick pulp.
3. To the cooked pulp, add the salt, sugar and the rest of the vinegar. Simmer the mixture for 20 minutes or so until it is thick. Remove from fire, cool and bottle.
Some vinegar may be added on top in each bottle. This helps to preserve it.