Preheat the oven to 350º F. Grease a 9″ x 13″ pan with butter.
In a small bowl, combine the mochiko, baking powder and cinnamon.
In a large bowl, whisk together the rest of the ingredients except the cinnamon sugar mix.
Add the dry ingredients to the wet ingredients, and whisk until smooth.
Pour the batter into the greased 9″ x 13″ pan, and use a spatula to smooth it out. Bang the pan on the counter once or twice to get rid of any air bubbles. Sprinkle the cinnamon sugar mix over the top, then bake it in the oven for 1 hour.
Let it cool completely, then cut into squares and serve. Enjoy!