Mix the flour, turmeric, salt, sugar and citric acid crystals in a bowl with a cup of water. With a whisk mix them together into a smooth paste.
Let this stand for 10 minutes. Meanwhile set up the steamer. You can use a large pot. Place an empty bowl in it as a stand on which to keep the plate. Grease a deep 'thali' that will fit into the pot easily leaving some space around. You need a lid to cover the pot tightly. You can tie the lid in a kitchen towel so that it will absorb the steam and not let water droplets fall into the batter while steaming.
After letting the batter stand for 10 minutes, add the soda bicarb into it. Mix it in by pulling at the batter with your fingers. The batter will get fluffy and soft, expanding in volume by almost 3 times [like beaten egg whites]Pour this batter into the greased thali. You can sprinkle sesame seeds on the batter. (Optional).
Keep the thali into the pot, cover with towel covered lid and steam for 20 minutes until a toothpick comes out clean.
Remove the thali from the pot and let cool for 5 minutes before cutting it into diamond / square pieces.
For tadka, heat one tsp of oil, put in the mustard seeds, sesame seeds and curry leaves. Once they splutter, turn it over the dhoklas.
Serve hot with tea.