Soak rice, daal and methi in water for 5-6 hours.
Grind fine, add salt and enough water to make a dropping consistency and leave to ferment 5-6 hours.
Heat tawa, and brush oil over it. When really hot, splash a little water over it, and pour about 1 cup of batter on to it.
It will spread a little. When the edges start browning a bit, pour a trail of oil around it.
Turn it over and let it brown on the other side too.
For an onion uttapam:
Before you turn the uttapam over, sprinkle a mixture of finely chopped onions, tomatoes, coriander leaves and green chillies.