Mix sugar and water in a saucepan and bring to a boil.
Measure rice flour in a bowl. Once the sugar and water is boiling, whisk is slowly into the rice flour.
It should create a smooth batter.
Allow the batter to cool until warm to the touch, about 110 degrees Fahrenheit / 43 Celcius.
You can speed this up by continuing to whisk it, or by pouring the batter back and forth between to bowls. The constant movement helps cool it down.
Add the yeast and mix. Let the batter rest for about 45 minutes to an hour.
You may need to mix the batter 10 minutes after adding the yeast to ensure it is fully dissolved and has mixed with the rest of the batter.
After about 30 minutes of resting, prepare your steamer. Add an inch of water to your pot and place your steamer and cake pan inside. Cover it and turn on to medium heat.
The cake pan should be hot to the touch when you add the batter in.
Pour the batter into the cake pan and steam for about 15 minutes. Then turn off the heat and keep the cake inside the steamer for another 10 minutes.
See NOTES for steaming tips!
Take the cake out and allow it to cool. Run a knife around the edges to remove and slice as desired.