1. Loosely chop and soak raisins in warm water, at least 10 to 15 minutes. (Use enough water to cover the raisins.) They can be soaked overnight. Drain off excess water prior to using.
2. In a food processor, puree raisins and brown sugar together. Add up to 1/4 c of buttermilk to help the mixture blend evenly.
3. In a large bowl, measure flour, salt, baking powder and cinnamon if using.
4. To that, add the pureed raisin mixture, and the remaining buttermilk. Mix thoroughly until all ingredients are thoroughly combined. Batter will be wet, like muffin batter.
Preheat oven to 325 degrees.
5. While oven is preheating, line a medium loaf pan with a parchment paper. (See photo.) Pour batter into parchment-lined medium loaf pan. Smooth the top with the back of a damp spatula.
6. Allow batter to rest in pan, before baking, at least 10 minutes. This allows the grains to better absorb the liquid in the batter.
7. Bake in a 325 degree oven for 45 minutes, or until internal temperature reaches 200 degrees.
8. Remove loaf pan from oven. Allow loaf to remain in pan for 10 minutes. Then life up on parchment paper to remove loaf from pan, and cool on a baking rack for one hour.