10-11 tbsp. brown rice flour
1 cup boosted brown rice starter
200 g. (1 1/4 cups) light buckwheat flour
1 cup plus 2 tbsp. water (maybe 3/4 cup if using eggs)
2 tbsp. flax meal (omit if using eggs) OR 2 eggs
1 c. maple syrup
1 tbsp. vanilla
1/2 cup oil (olive works, canola is milder)
1/2 tsp. salt
1/4 c. arrowroot
1 1/2 tbsp. baking powder
The night before baking, mix together the first four ingredients. Dough will be very stiff, and you'll have to poke and prod and knead to get all the flour moistened. Cover bowl tightly with plastic wrap and let it sit at room temperature for 12-18 hours.
Next day, preheat oven to 350f. Oil a springform 10" pan, and line the bottom with oiled parchment.
Mix flax meal or eggs, maple syrup, vanilla, oil, and salt together. In a separate small bowl, combine the arrowroot and baking powder.
Add the maple syrup mixture to the fermented dough, and stir well to combine. When you've got a well-mixed batter, add the arrowroot/baking powder mixture and use as few strokes as possible to incorporate all the white powdery bits.
Pour batter into the pan and bake 30-40 minutes, until a toothpick comes out fairly clean and the top of the cake is golden brown.
Remove sides of springform pan, and let the cake cool fully before slicing.