Make sugar water: In a small pot, heat 2 cups water + 1 cup sugar until the sugar dissolves completely. Remove from heat and let cool to room temperature.
Bloom the yeast: In a small cup, mix 1 tsp yeast + 2 tbsp warm water (105–110°F). Let sit 5–10 minutes until foamy.
Mix the batter: In a large bowl, add 2 cups rice flour. Pour in the cooled sugar water and whisk until smooth. Add the bloomed yeast mixture and stir gently until combined.
Proof: Cover and let proof in a warm spot for 2–3 hours, until a thick layer of small bubbles forms across the surface.Optional: At about 30 minutes into proofing, gently fold in 1/8 tsp oil for added moisture.
Prep pan: Lightly grease a 9-inch round cake pan (or similar-sized metal pie pan). Pour the batter into the pan.
Steam: Bring steamer water to a steady strong steam first. Place the pan on the rack, cover, and steam for 18–25 minutes, depending on pan thickness, batter depth, and elevation.
Check doneness + cool: Toothpick in the center should come out clean. Remove from steamer and let cool completely before removing from the pan and slicing into diamonds, wedges, or cubes. Serve and enjoy!
Notes
Oil: I add the 1/8 tsp oil to help keep the cake slightly more moist.
Avoid a goopy top: Condensation from the lid can drip onto the cake. Wrap the lid with a towel to absorb moisture. (If using a bamboo steamer/lid, you can usually skip this because bamboo absorbs condensation.)
Steam time tip: If your cake is set on the edges but the center still feels dense, steam 3–5 minutes longer and check again.