Heat oil in cooking pot. Add mustard seeds and curry leaves [stand back as they spurt], which release a mustard aroma. Turn heat on low and add onions. Fry till brown, stirring occasionally. Then add TOMATO KASAUNDI . Stir and add cooked lentils. Heat through and taste for salt. Add optional ingredients if desired and mix well.
Serve on a bed of steaming hot rice or with chapatis, accompanied by Goan Cuisine Cucumber Archar.