This is very famous in the chain of shops in Madurai called Murugan Idli Kadai.
For this, exclusivey small onions ( chinna vengayam ) have to be used for the best flavour. They are first peeled & very thinly sliced. A sharp potato slicer does the job best. This way, just a few onions give a good volume of slices which are spread out in the oothappam.
This dish must be eaten hot.
The accompaniments can be milakai podi or any chutney. In Madurai it is served with 6 side dishes - milakai podi & oil, sambar, coconut chutney, pudina or coriander chutney, ginger chutney and tomato chutney.

Dosa batter - 2 cups ( can be venthaya dosai or turdhal oothappam or ordinary dosai batter)

Small onions - 20 – 25

Oil - to make oothappams

The batter can be a little more sour than for dosai, medium thick and not watery.

Add the thinly sliced onions & mix well.

Make oothappams, the usual way, roasting with a little oil on both sides.

Serve hot with any chutney.