Preheat your oven to 375°F (190°C). Prepare a muffin tin by lining it with paper liners or lightly greasing it with cooking spray.
In a medium bowl, combine the finely chopped cranberries with the zest of the orange. Mix well and set aside to allow the flavors to meld.
In a large mixing bowl, whisk together the all-purpose flour, granulated sugar, brown sugar, baking powder, baking soda, and salt until evenly mixed and free of lumps.
In a separate bowl, crack the egg and beat it thoroughly. Add the vegetable oil, buttermilk, orange juice, and vanilla extract. Whisk these ingredients together until they are smooth and fully combined.
Make a well in the center of the dry ingredient mixture and pour the wet ingredients into it. Gently stir the mixture using a spatula or wooden spoon until just combined; it's important to avoid overmixing to keep the muffins fluffy.
Carefully fold in the cranberry and orange zest mixture until they are evenly distributed throughout the muffin batter.
Using a serving spoon or an ice cream scoop, evenly divide the muffin batter among the prepared muffin cups, filling each about ¾ of the way full to allow for rising.
Bake in the preheated oven for 18-20 minutes, or until a toothpick inserted into the center of a muffin comes out clean and the tops are lightly golden.
Once baked to perfection, remove the muffins from the oven. Let them cool in the tin for 5 minutes, then carefully transfer them to a wire rack to cool completely.
Notes
Serve warm on a decorative platter, garnished with fresh cranberries and orange slices.