Preheat your oven to 350°F (175°C). Grease the loaf pan or line it with parchment paper for easy removal.
In a mixing bowl, whisk together the flour, sugar, baking powder, baking soda, salt, and orange zest until well combined.
In a separate bowl, beat the eggs, then add the milk and melted butter, mixing until smooth.
Slowly pour the wet ingredients into the dry ingredients, stirring gently until just combined. Be careful not to overmix; a few lumps are okay.
Fold in the chopped cranberries and nuts (if using) until evenly distributed.
Pour the batter into the prepared loaf pan, smoothing the top with a spatula.
Bake in the preheated oven for 55-60 minutes, or until a toothpick inserted into the center comes out clean.
Once baked, remove from the oven and let it cool in the pan for about 10 minutes. Turn out onto a wire rack to cool completely.
Slice and serve as desired.