01 - Set the oven to 375°F and arrange paper liners in a 12-cup muffin tin.
02 - In a large bowl, whisk together flour, sugar, baking powder, baking soda, and salt until evenly distributed.
03 - In a separate bowl, whisk vegetable oil, eggs, buttermilk, vanilla extract, and orange zest (if using) until smooth.
04 - Pour the wet ingredients into the dry and gently fold together until just combined, taking care not to overmix.
05 - Fold in the cranberries evenly into the batter.
06 - Spoon batter into the prepared muffin tin, filling each cup about three-quarters full.
07 - Bake for 20 to 22 minutes or until a toothpick inserted at the center comes out clean.
08 - Allow muffins to cool in the tin for 5 minutes, then transfer to a wire rack to cool completely.