Preheat the oven to 375°F (190°C). Grease or line a muffin tin with paper liners.
In a large mixing bowl, whisk together the flour, baking powder, baking soda, salt, and sugar.
Stir in the orange zest and chopped cranberries until evenly distributed.
In a separate bowl, beat the egg and then mix in the buttermilk, vegetable oil, and vanilla extract.
Pour the wet ingredients into the dry ingredients, gently mixing until just combined. Be careful not to overmix; it’s okay if there are a few lumps.
Divide the batter evenly among the 12 muffin cups, filling each about two-thirds full.
Bake in the preheated oven for 18-20 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
Once baked, remove the muffins from the oven and allow them to cool in the pan for 5 minutes before transferring them to a wire rack to cool completely.