Preheat oven to 175°C (350°F) and grease a loaf or bundt pan.
In a bowl, cream butter and sugar until light and fluffy.
Add eggs one at a time, mixing well after each addition.
Stir in orange juice and orange zest.
Sift flour and baking powder together, then fold into the wet mixture.
Pour batter into the prepared pan and smooth the top.
Bake for 50–60 minutes or until a toothpick inserted comes out clean.
Let cool before slicing and serving.