Preheat the oven to 400℉. Use a grater or citrus zester to zest the medium orange and set the zest aside.
In a large mixing bowl, mix flour, sugar, baking powder, and salt with a wooden spoon.
Add the egg, orange juice, orange zest, vanilla extract, and buttermilk. Mix until combined. Grate the butter into the mixing bowl. Finally, add the cranberries.
Use your hands to work the ingredients together: flattening the dough, then folding it onto itself similar to folding a piece of paper in half. This adds buttery layers to the scones.
Once the butter and cranberries are evenly distributed in the dough, roll it into a ball. Lightly flour a surface and flatten the scone into a disk about 12" in diameter. Cover with plastic wrap or transfer to a gallon-size Ziploc bag and put it in the fridge to chill for 20-30 minutes.
Once chilled, return the dough to the lightly floured surface and cut it into 8 slices. Use your hand or a pastry brush to brush the top of the scones with heavy cream or milk. Move them onto a parchment paper-lined baking sheet, separating them 1 inch apart. Bake them for about 25 minutes. They'll be ready when the tops of the scones are golden brown. Allow the scones to cool for 10-15 minutes on a wire rack.