- Preheat your oven to 375°F (190°C). Grease a muffin tin or line with paper liners. 
- In a large bowl, mix wheat bran and buttermilk. Let it sit for 10 minutes. 
- In another bowl, whisk together oil, egg, brown sugar, and vanilla extract. 
- Add the wet ingredients to the bran mixture and stir until combined. 
- In a separate bowl, combine flour, baking soda, baking powder, and salt. Add to the bran mixture and stir until just combined. 
- Fold in the raisins. 
- Spoon the batter into the prepared muffin tin, filling each cup about ⅔ full. 
- Bake for 15-20 minutes, or until a toothpick inserted into the center of a muffin comes out clean. 
- Let the muffins cool in the tin for a few minutes, then transfer to a wire rack to cool completely.