Preheat oven to 170°C fan forced. Grease and line a 20cm round cake tin with baking paper. In a large bowl, beat the butter and sugar until pale and fluffy.
Add the eggs one at a time, mixing well between each addition.
Stir through the yoghurt, orange zest, orange juice and vanilla extract.
Gently fold through the flour, baking powder and salt until just combined.
Pour into the prepared cake tin and bake for 40 minutes, or until a skewer inserted into the centre comes out clean.
While the cake is baking, prepare the orange syrup by adding all syrup ingredients to a small saucepan. Bring to a boil, then reduce heat and simmer gently for 10 minutes, or until thickened and sticky.
Use a skewer to poke holes over the top of the cake and slowly pour over the syrup. Allow the syrup to soak in for 10 minutes before removing the cake from the tin and transferring to a wire rack to cool completely.
Serve with fresh oranges.
