Whisk your eggs, sugar, orange juice, baking powder and butter until fluffy and creamy, in a separate bowl sift your flour and add your cinnamon, orange zest and mix evenly, create a well and add your wet ingredients into your dry.
Whisk evenly until smooth. In a loaf tin grease with some extra butter and pour cake batter intoo dish and bake for 35 minutes at 180 degrees centigrade.
After it has risen and browned, remove from the oven and allow to cook for 15 minutes.
Dust with icing sugar and place lemon slices on top and serve.