01 - Preheat the oven to 350°F. Grease and flour a 9x5-inch loaf pan or line it with parchment paper.
02 - In a large bowl, whisk together the flour, sugar, baking powder, baking soda, and salt until evenly distributed.
03 - In a separate bowl, beat the eggs, then whisk in the vegetable oil, buttermilk, and vanilla extract until smooth.
04 - Pour the wet ingredients into the dry ingredients and stir gently until just combined, taking care not to overmix.
05 - Fold in the cranberries, walnuts, and orange zest if using, ensuring even distribution throughout the batter.
06 - Pour the batter into the prepared loaf pan and smooth the surface evenly.
07 - Bake for 50 to 60 minutes, or until a toothpick inserted into the center comes out clean.
08 - Allow to cool in the pan for 10 minutes, then transfer to a wire rack to cool completely before slicing.