Wash, clean and dice the tomatoes. Peel and chop shallots and garlic. Heat oil in a pot. Sauté shallots and garlic in it. Add the tomatoes and steam briefly.
Add vinegar, brown sugar, ketchup, 6 tablespoons of water, chilli and curry powder. Simmer over medium heat, stirring occasionally, for 20-25 minutes until the sauce thickens a little. Season the sauce to taste with salt, chilli and curry powder and possibly a little vinegar.
Pour into glasses or bottles while still hot. Seal tightly. Keeps in the refrigerator for at least 2-3 weeks. Goes well with grilled meat and vegetables.