Heat the oil in a pan. Fry mustard seeds, urad dal, curry leaves, garlic, fenugreek seeds and red chillies until the urad dal turns golden brown. Using a slotted spoon, remove these ingredients into a small bowl and keep aside.
In the same pan, fry the chopped tomatoes on high flame with salt and turmeric, until it turns mushy. Allow this to cool.
Transfer the cooked tomatoes to a mixer jar / food processor. Add the fried spices to this along with coriander and grind to a coarse or fine paste, as per your liking.
You can also reserve 1 tsp of the fried mustard, urad dal and curry leaves to use as a garnish on top of the chutney. Save in an airtight container in the refrigerator. Use within 2-3 days.
Serve this tomato chutney with idli, dosa, parathas or even toast.