To a blender, add the tomatoes, roughly chopped onions, salt, dry red chillies and blend to almost smooth blend.
Heat a deep pot with a lid or a kadai, and add oil to it and once hot, add the mustard seeds and allow it to crackle fully, add the cumin and fennel seeds and allow it to sizzle for a couple of seconds.
Quickly add the blended onion and tomato mixture, turmeric powder, fennel seed powder. Once you add it will bubble so keep it covered and cook for 5 - 10 mins on medium flame.
Open the lid and give it a stir and cook for 5 more minutes. The chutney will be brighter in red and not very thin not too thick.
Serve it hot over idles or dosa and enjoy !!!
Keyword chutney, dosa side dish, Idli dosa, Spicy chutney