Step 1: Heat the oil and butter in a pan on medium heat.
Once hot add onions. Sauté it till it turns translucent.
Step 2: Then add tomatoes, ginger paste, and turmeric powder. Mix well. Cook it till oil leaves from the mixture. Using back of your spoon just mash the tomatoes and make it kind of gravy. Then add black salt, pav bhaji masala, lemon juice and salt. (Be careful while adding salt because idli has salt already and we added black salt.) Mix well.
Step 3: Add idli pieces. Mix gently.
Step 4: Garnish with cilantro leaves and serve hot.