Preparing the Chutney Base

In a pan, heat 1 tbsp of oil.
Add the garlic cloves and sauté for about 30 seconds.
Add the dry red chillies and sauté until they change colour, being careful not to burn them.
Add the sliced onions to the pan and sauté until they turn translucent.
Once the onions are cooked, add the chopped tomatoes. Cook until the tomatoes turn soft and mushy.
Turn off the heat and allow the mixture to cool.

Grinding:

Transfer the cooled mixture to a blender or mixer grinder.
Add salt to taste.
Grind to a slightly coarse or smooth paste as per your preference, adding water as needed to aid the grinding.

Tempering:

In the same pan, heat 1 tsp of oil.
Add the mustard seeds, and curry leaves, sauté for a few seconds.
Pour this tempering over the prepared chutney and mix well.

Serving:

Transfer the Kara chutney to a serving bowl.
Serve it as an accompaniment with idli, dosa, or even chapati.

The chutney might be pretty spicy, given the number of chillies. You can adjust the quantity based on your spice tolerance. If the chutney is too spicy, add a pinch of jaggery or sugar to balance the flavours. Always remember to adjust ingredients based on personal preference!