In a mixing bowl, combine the rice flour, water, granulated sugar, active dry yeast, baking powder, and vanilla extract (if using).

Whisk or stir the mixture until the ingredients are well combined and the batter is smooth and lump-free.

Let the batter rest at room temperature for about 30 minutes to allow the yeast to activate and ferment. The batter will rise slightly during this time.

While the batter is resting, prepare the steamer by filling the pot with water and bringing it to a boil. Place the cake pan or dish inside the steamer.

Once the batter has fermented, give it a quick stir and pour it into the greased cake pan or dish, filling it about three-fourths full.

Place the steamer with the cake pan inside over the boiling water.

Cover the steamer with a lid and steam the rice cake over medium heat for about 25-30 minutes or until a toothpick inserted into the center comes out clean.

Carefully remove the steamer lid, taking care to avoid any condensation from dripping onto the cake.

Using oven mitts or kitchen towels, carefully remove the cake pan from the steamer and let it cool for a few minutes.

Once the rice cake has cooled slightly, run a knife around the edges of the cake pan to loosen the cake.

Invert the cake pan onto a plate or serving dish to release the steamed rice cake.

Cut the cake into desired slices or squares.

Serve the steamed rice cake warm or at room temperature.