- Preheat the oven to 325°F and grease a 9x5-inch loaf pan.
- In a large bowl, whisk the brown sugar, buttermilk, vegetable oil and egg together.
- In a separate bowl, soft the flour, baking powder, salt, cinnamon (or cardamom) and baking soda. Add this to the liquids and stir just until blended. Stir in the rhubarb and pecan pieces. Scrape the batter into the prepared pan and bake for about 60 minutes, until a tester inserted in the center of the loaf comes out clean. Cool the cake for 40 minutes in the pan, then turn out to cool completely.