First boil tomatoes with 1 cup water.
Add green chilly and salt to this and boil for 5 minutes.
Grind coconut,cumin seeds,onion ,chilly powder and turmeric powder in a mixer.
Add this ground mix to tomato mix.
Add butter milk to this .
mix well and boil for a minute.
Heat oil in another kadai add mustard's,when it splutters add fennel seeds,curry leaves and red chilly,saute for a minute.
Add this tempering to tomato curry.
Now special tomato moru curry is ready.