Preheat your oven to 350°F (175°C) and lightly grease your loaf pan with cooking spray. This prevents the cake from sticking and ensures even baking.
In a medium bowl, whisk together the flour, baking powder, and salt. This helps the leavening distribute evenly and keeps the cake light.
In a large bowl, beat butter and sugar until smooth and fluffy. Add eggs one at a time, then mix in the orange zest, juice, and sour cream. This combination gives the cake a soft, moist texture.
Gradually fold in the dry ingredients until fully incorporated. Avoid overmixing; otherwise, the cake can turn dense.
Pour the batter into the prepared pan and bake for 50–60 minutes. Check doneness with a toothpick; it should come out clean. Let the cake cool on a rack before glazing.
Mix confectioners’ sugar and mandarin juice in a small bowl. Adjust for desired consistency, then pour over the cooled cake. Sprinkle extra zest for a bright finish.