I got this idea when I was making guntaponglu (in telugu) or paniyaram (in tamil), which is made from dosa batter, in which some fried onions and other ingredients are added.
With the same batter I just tried to make the dosa, for a change, as the batter was left and I was thinking not to make guntaponglu again. So I call this dosa as thadka dosa. You can do this with the dosa batter also .For the batter you can use my previous 2 idli recipes in which rice is used and dosa recipe also. The recipe which iam giving is for the idli batter and dosa batter. Idlis are the best in this batter, but after 2 days, I start making uttapam and dosa for a change. You can use your own dosa batter also and make uttapam and thadka dosa.
For making batter
Making tadka dosa