Preheat your oven to 350°F (175°C). Grease a 9x5-inch loaf pan and line with parchment paper, leaving overhang on the sides for easy removal.
In a large bowl, whisk together the flour, sugar, baking powder, baking soda, and salt until well combined.
Rinse fresh cranberries and pat them dry. If they're particularly tart, toss them with 1 tablespoon of the sugar from the recipe.
In a separate medium bowl, whisk together the melted butter, egg, orange juice, and orange zest until well combined.
Pour the wet ingredients into the dry ingredients and stir just until combined—about 15-20 strokes. Be careful not to overmix.
Gently fold in the cranberries and nuts (if using) with a spatula. For visual appeal, reserve a small handful of cranberries to sprinkle on top of the batter.
Transfer the batter to the prepared loaf pan and smooth the top. Bake in the preheated oven for 50-60 minutes, or until a toothpick inserted in the center comes out clean with a few moist crumbs. If the top browns too quickly, loosely cover with aluminum foil after 35 minutes.
Allow the bread to cool in the pan for 15 minutes, then lift out using the parchment overhang and transfer to a wire rack to cool completely (about 30 minutes).
While the bread cools, prepare the glaze by whisking together powdered sugar, orange juice, and zest until smooth. Start with 1 tablespoon of juice and add more if needed to reach desired consistency.
Drizzle the glaze over the completely cooled bread for a professional-looking finish that adds a burst of citrus flavor.