01 - Preheat oven to 375°F and line a 12-cup muffin tin with paper liners.
02 - In a large bowl, whisk together the flour, sugar, baking powder, baking soda, and salt.
03 - In a separate bowl, whisk together the vegetable oil, eggs, buttermilk, vanilla extract, and orange zest if using until smooth.
04 - Pour the wet mixture into the dry ingredients and gently fold until just combined, avoiding overmixing.
05 - Fold in the cranberries carefully to distribute evenly.
06 - Divide the batter evenly among the muffin cups, filling each about three-quarters full.
07 - Bake for 20 to 22 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
08 - Allow muffins to cool in the pan for 5 minutes before transferring to a wire rack to cool completely.