This is what you need :
Arbi / Colocassia (medium size) : 250 gm
Green tomato : 2 medium - sliced thinly
Ajwain( carom seed) : 1/3 of tea spoon
Onion : 1 medium - sliced thinly
Amchur powder / chat masala - 1 tea spoon
Red chilli whole (deseeded ) : 2-3 small
Garlic 2-3 cloves - finely slice
Oil: 1 tbs ( mustard or any cooking oil)
Now boil the arbi in pressure cooker for one whistle, remove from heat, drain and leave aside to cool.
Finely slice onion, tomatoes , garlic . Make a incision in chilli and remove seeds ( it gives a nice someky flavour without the heat)
Once arbi is cooled enough to handle, peel the skin ( be careful at this stage some variety really itches, in that case rub oil and lemon juice on hands before handling arbi)
Slice up boiled arbi in 4/6 pieces length wise.
Now heat oil in wok, once it smokes turn down the heat to low for a minute, add ajwain seeds, garlic , red chilli and fry for 30 seconds.
Turn the heat to medium
Add onion and fry for 2-3 minutes till it turns brown.
Add sliced tomatoes, turmeric powder , fry for minute , cover and cook on low heat for 3-4 minutes.
Add arbi and mix well so masala covers completely .
Cover and cook for 3-4 minutes on low heat till arbi is almost done
Add chat masala / amchur powder and salt and cook for 2-3 minutes till arbi is done.
Serve hot with roti / paratha