Preheat your oven to 180°C (350°F). Grease and line a loaf tin with baking paper for easy removal.
In a large mixing bowl, beat together the softened butter and caster sugar using an electric mixer until the mixture is light and fluffy. This should take about 4-5 minutes.
Add the eggs one at a time, mixing well after each addition. If the mixture looks a bit curdled, don’t worry – it will come together once the flour is added.
Gently fold in the finely grated orange zest and orange juice, allowing the bright flavors to infuse the batter.
Sift the self-raising flour over the mixture and fold it in gently using a spatula. Be careful not to over-mix, as this can lead to a dense cake.
Pour the batter into the prepared loaf tin, smoothing the top with a spatula.
Bake in the preheated oven for 45-50 minutes, or until a skewer inserted into the center comes out clean. Keep an eye on it; if the top starts browning too quickly, cover it with foil.
While the cake is baking, mix the 85 grams of caster sugar with the juice of the remaining orange in a small bowl until the sugar is dissolved.
Once the cake is out of the oven, let it cool in the tin for about 10 minutes before transferring it to a cooling rack. While it’s still warm, poke holes in the top of the cake with a skewer and drizzle the orange syrup over it. Allow the cake to absorb the syrup as it cools completely.
