Wash the tomatoes and cut them into pieces. Peel and finely dice the shallots and garlic
Heat the oil in a pot. Sauté shallots and garlic until translucent. Sauté the curry in it. Add the tomatoes and sauté. Stir in vinegar, sugar, ketchup, 6 tbsp. water and chilli powder. Bring to the boil and reduce over medium heat, stirring frequently, for 20-25 minutes until thick
Season the sauce with salt, chilli powder, curry and possibly some vinegar. Pour it still hot into clean glasses or bottles, close them tightly immediately