Preheat the oven to 180ºC/fan 160ºC/gas mark 4. Put the butter, sugar, flour and eggs in a bowl and, using an electric hand mixer, beat until thoroughly combined. Stir in the orange zest, 1 tbsp juice and the yogurt.
Spoon the mixture into a deep 20cm cake tin, lightly greased and lined with baking parchment. Bake the cake for 50-55 minutes until risen and golden and a skewer inserted into the middle comes out clean. Cool in the tin for 10 minutes, then turn out, remove the paper and cool completely on a wire rack.
Meanwhile, bring a pan of water to the boil, add the sliced orange zest and boil for 1 minute until the zest starts to soften. Dry on kitchen paper. Once the cake has cooled, dust with icing sugar and decorate with the strips of orange zest.