Halve tomatoes, deseed and make a puree in a blender to get a yield of 1.2 kgs or else adjust the quantity of tomatoes used to make puree. Tie up cloves, cinnamon, green cardamoms, cumin seeds and peppercorns in a piece of muslin cloth to make a potli. Pour tomato puree into a deep pan.
Place spice potli in it and cook on medium heat. Add finely chopped ginger and onion and continue cooking. Add one third of the sugar and stir. Add salt, red chilli powder and cook till the mixture reduces to one third of its original quantity.
Add remaining sugar and continue to cook till water does not separate. To test pour a spoonful on a plate. If the water does not separate the right consistency has been reached. Mix sodium benzoate in a little water.
Remove spice potli from the mixture, squeezing it to extract all the flavours. Strain the mixture through a strainer. Add acetic acid and sodium benzoate and mix well. Pour into dry and hot sterilized bottles taking care not to fill till the rim of the bottles.
You can further pasteurize the filled bottles for thirty to thirty five minutes in hot water at 85°C to 88°C.
Chef TipTo get a smoother, free flowing consistency you can add about one and a half tablespoons of cornstarch dissolved in a little water while cooking.