You can make it on the Tawa too. Heat the tawa for 10 minutes on slow with a heavy vessel like a thick aluminium one inverted on it. Your cake tin should be such size that can be placed on the tawa...Say upto 1/2 kg only. After 10 minutes, remove the vessel, place a ring on the tawa n place ur tin and cover with vessel again.Work fast for this step. Takes same time as in the otg.