Soak dal for four to six hours and grind it with yogurt.
Transfer into a deep bowl. Add green chillies, spinach puree, salt, sugar and asafoetida and mix well. Mix fruit salt in lemon juice and add to the batter and mix.
Add oil and mix. Grease dhokla plates. Heat sufficient water in the steamer pot. Pour the batter into the dhokla plates, fit them on the stand and place the stand in the steamer. Close the lid and steam for fifteen minutes or till done.
Cool slightly, cut into pieces and serve garnished as per your taste.