When they start to pop, add urad dal and fry for 1 - 2 minutes.
Add finely sliced onion and fry for 3 minutes till golden colour.
Add finely sliced tomatoes and mix well.
Add curry leaves, red chilli powder, sambar powder and turmeric powder and mix all the ingredients well.
Add salt to taste and 1 tbsp water. Cover with a lid and cook on a low heat for 10 - 12 minutes or till tomato - onion mixture well blended with spices and thickens. Garnish with chopped coriander leaves.
Serve as a side dish with rice / paratha / rotis / sambar rice.