Preheat your oven to 350°F (175°C). Grease a 9x5 inch loaf pan and line it with parchment paper for easy removal.
In a large bowl, whisk together the flour, sugar, baking powder, baking soda, salt, and cinnamon (if using).
In another bowl, mix the melted butter, egg, orange juice, and orange zest.
Pour the wet ingredients into the dry and stir until just combined. Don't overmix – a few lumps are okay!
Gently fold in the cranberries.
Pour the batter into your prepared pan and smooth the top.
Bake for 60-70 minutes, or until a toothpick inserted into the center comes out clean.
Let the bread cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.
While the bread is cooling, make the glaze: In a bowl, whisk together the powdered sugar, 2 tablespoons of orange juice, and the orange zest. Add more orange juice if needed to reach a pourable consistency.
Once the bread is completely cool, drizzle the glaze over the top.
Let the glaze set for a few minutes before slicing and serving.