In a mixer, whisk the butter, sugar and lemon zest until pale and light.
Add the eggs one by one, beating well after each is added.
Sift the flour and baking powder and add to the butter mixture. Fold in the coconut and the sour cream.
Pour the mixture into the prepared tin and bake for 35 minutes or until a skewer inserted into the middle of the cake comes out clean.
Cool the cake completely and then store in an airtight container.
Combine the sugar, vanilla bean, lemon juice and water in a heavy-based sauce-pan. Over a high heat, bring to the boil without stirring.
Continue to boil the sugar till the large bubbles have reduced to tiny bubbles (about 10 minutes). Add the raspberries and stir rapidly until combined. Bring the syrup back to the boil and then simmer for 5 minutes.
Allow the syrup to cool then pour into an airtight container until ready to use. Pour over the cake at the last minute.