Preheat the oven to 375F. Grease a 12-cup muffin tin or line with paper liners.
In a large mixing bowl, stir together the wheat bran and the buttermilk. Let stand for 10 minutes.
Meanwhile, in a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Stir in the raisins.
After 10 minutes, whisk the sugar, oil, egg, and vanilla into the bran mixture. Add the flour mixture and stir together until just combined. Divide the batter among the muffin cups (about ¼ cup each).
Bake for 20 minutes or until a toothpick inserted into the center comes out clean. Let cool for 10 minutes before serving.
Video
Notes
Use an ice cream scoop or measuring spoon to scoop the batter for even-sized muffins.
Measure your flour and wheat bran correctly by using a scale! Adding too much flour or wheat bran to the recipe is the most common reason the muffins end up dense. The best and easiest way to measure the ingredients is by using a scale.
Don’t skip soaking the wheat bran cereal, as it helps soften it. It’ll also help the muffins rise better as they are less likely to cut through the gluten.
Don’t overmix the batter, as it’ll lead to the muffins becoming dense and heavy.
Bring your eggs to room temperature, so they incorporate fully into the batter without overmixing.
Make sure your brown sugar isn’t lumpy. See my post on how to soften brown sugar if your brown sugar has hardened or has lumps in it.