Chop the onion to fine bits and keep aside separately.
Cut both the chilies into slivers and set aside.
To cook:
Set a wok on high heat.
Pour in the oil and throw in the mustard seeds.
As soon as the mustard seeds are about to finish popping, lower the heat and tip in the cumin seeds. Stir just once and put in the chilies (both types).
Pull the curry leaves off their sprigs and throw them in.
Stir and chuck in the tomatoes. Add the salt and turn up the heat.
As soon as the tomatoes are hot, turn down the heat and cover with a lid.
Cook for 5 minutes, taking care to stir occasionally.
Switch off the heat and take off the lid. Let the tomatoes cool down for 5 minutes.
Tip in the chopped onion and pour in the curd.
Stir and serve warm over a pile of steaming hot rice. If you are a coriander lover, do garnish with coriander leaves. Enjoy!