Preheat oven to 160°C. Brush a 25cm (top measurement) pan with melted butter to lightly grease. Combine the orange juice, yoghurt and poppy seeds in a small bowl.
Use an electric beater to beat the butter, caster sugar and orange rind in a large bowl until pale and creamy. Add the eggs, 1 at a time, beating well after each addition until just combined.
Sift the flour and baking powder over the egg mixture. Add the yoghurt mixture and use a large metal spoon to fold until just combined. Spoon mixture into the prepared pan and smooth the surface. Bake in oven for 1 hour or until a skewer inserted into the cake comes out clean. Set aside for 5 minutes to cool slightly. Turn onto a wire rack to cool completely.
Use a zester to remove the rind from the orange. (Alternatively, use a vegetable peeler to peel rind from the orange. Use a small sharp knife to remove white pith from the rind. Cut rind into thin strips.) Combine the icing sugar and extra orange juice in a bowl until smooth. Pour over the cake and sprinkle with the orange rind. Set aside for 20 minutes or until the icing is set.