Preheat the oven to 375°F (190°C). Line a 12-cup muffin tin with paper liners or lightly grease each cup.
In a large mixing bowl, whisk together flour, sugar, baking powder, baking soda, salt, and cinnamon.
In another bowl, whisk together melted butter, eggs, vanilla extract, buttermilk, and orange zest until smooth.
Pour the wet mixture into the dry ingredients. Stir gently until just combined—do not overmix.
Fold in cranberries until evenly distributed throughout the batter.
Divide the batter evenly among the muffin cups, filling each about three-quarters full.
In a small bowl, mix sugar and cinnamon for the topping, then sprinkle over the muffins.
Bake for 18–22 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
Let the muffins cool in the pan for 5 minutes before transferring them to a wire rack to cool completely.
