In a small bowl, add turmeric powder, lemon juice and salt to it. Mix well with a fork.
Heat oil in a pan, add mustard seeds, when they splutter, add all the rest of the ingredients listed under " To Temper " Saute for a min until dal turns golden brown.
In a medium flame, add the lemon juice mix, give a quick stir and add plain idiyappam and mix well. Turn off the stove.