Grease a thali and keep aside.Sieve the besan twice, tip into a clean bowl.
Add water slowly to make a thick but flowing batter.
Leave for 30 minutes.
Now add turmeric, lemon juice, ginger-chilli and salt to the besan batter and mix well.
Heat about 2 cups water in the cooker and place a stand on it. The water level should be below the stand and let it come to a rolling boil.
When the water is boiling, quickly add the Eno fruit salt to the besan batter and give a quick whisk, it will be bubbly and frothy, immediately pour into greased thali and place inside cooker.Close lid of the cooker and remove whistle.
Let steam without whistle for 20-30 minutes or till done(test with toothpick, it should come out clean).
Meanwhile prepare the tempering/tadka- heat oil in a small pan, add mustard seeds and let sputter. Add split green chillies, the lemon juice and sugar plus a little water till it forms a syrupy solution. Taste and adjust lemon juice/sugar
Once dhokla is done, take out and let cool. Pour the syrup on top and let soak for an hour.
Garnish with coconut and coriander leaves. Chill and serve