Heat oil in a pan.

Add mustard seeds and when they begin to splutter, add chopped onions, curry leaves and saute till light brown, on a low flame.

Add green chillies, red chilly powder, turmeric powder and cook for a few minutes.

Add sliced tomatoes and cook, till your required standard.

Switch off the flame.

Add tomato ketchup and stir well.

:- Serve hot with rotis.