Dry roast the tomatoes in a skillet until nicely roasted on all sides. Remove the tomatoes and add the red chilies to the skillet. Dry roast the chilies until charred.
Let the tomatoes and chilies cool. Peel the tomatoes; chop both the tomatoes and chilies. Reserve all the tomato juice.
Heat 1tbsp oil in a sauce pan, add the mustard and fenugreek seeds. Once the seeds start to splutter, add the grated ginger and sliced garlic. Cook till the garlic is lightly browned all over. Add the chopped tomatoes, chilies, reserved tomato juice, ground cumin, ground coriander, turmeric and salt.
Cook on medium flame until all the water is evaporated and the chutney gets a nice thick consistency.