heat oil, crackle mustard seeds, fenugreek seeds and saute garlic till brown
add chopped tomatoes and salt. fry till mushy.
when the tomatoes are mushy, add turmeric powder, chilli powder and cook in simmer till it thickens and reduces to less than half the initial quantity leaving out oil on all sides.
finally switch off and add jaggery. mix well.
store in air tight container and refrigerate to use it later.