Blanch tomatoes in boiling water for two minutes and drain. Peel and chop roughly. Combine sugar and citric acid with two cups of water in a pan. Cook, uncovered, on low heat for ten minutes. Add the tomatoes and cook further till thick. Add vinegar and continue to cook for five minutes. Heat oil and sauté onions till translucent. Remove into a bowl and set aside.
In the same pan add butter and sauté garlic till light brown and crisp in texture. Set aside. Add sautéed onions, fried garlic, salt, crushed roasted cumin seeds, onion seeds and red chilli powder to the cooked tomatoes. Mix well. Cool and store in sterilized bottles.