Blend the soda and molasses until light and foamy. Set aside.
In another bowl, combine the margarine and brown sugar, then mix in the eggs along with the rice bran and rice flour.
To the molasses mixture, add the buttermilk and stir well. Then add this to the brown sugar mixture, and mix well.
Pour into greased/paper lined muffin tins and fill 3/4 full. Bake at 375°F for about 30 minutes, or until internal temperature of muffin reaches 205°F, using an instant read thermometer.
Notes
[hr]To Make Buttermilk: put 1 Tbsp vinegar into measuring cup and add whole milk (or milk alternative) to bring to 1 cup - let stand 5 minutes. [hr]