Heat oil in a saucepan. Fry the curry leaves, then add in the onions, green chillies and potatoes and saute for around 5 minutes.
Add in the masala powders and saute for a minute, or till the raw smell goes.
Now add in the tomato peices along with salt and water and cook with the lid closed till the potatoes are done and the gravy is thickened.
Serve warm with rotis...