Preheat the oven to 180°C/ 160°C/Gas Mark 4. Lightly butter the base and sides of a 900g loaf tin, line with greaseproof paper and set to one side. Place the butter and Golden Caster Sugar in a large Mason Cash bowl and beat with an electric whisk until pale and fluffy.
Add the lime zest and then add the eggs, a little at a time, whisking well in between each addition. Sift the flour over the egg mixture and then add the desiccated coconut. Beat together with a wooden spoon until thoroughly combined. Add the coconut milk and beat again with the wooden spoon.
Pour into the prepared loaf tin and level off the top. Bake for 55 minutes until golden and risen, check the loaf is done by inserting skewer (it should come out clean). Meanwhile, place the lime juice, Golden Caster Sugar and rum in a small saucepan and heat very gently until dissolved, then remove from heat.
Lightly prick the top of the baked cake with a skewer. Drizzle the lime and sugar mixture all over the top of the cake, scatter over the flaked coconut and allow to stand in the tin for 10 minutes. Carefully remove from the tin and allow to cool completely on a wire rack. Slice and serve or store in an airtight tin for up to two days.
If you don’t have any flaked coconut, simply scatter the finished cake with 3 tbsp toasted desiccated coconut.
Any left over coconut milk can be stored in an airtight container in the fridge for up to a week or alternatively, pour into a freezer bag and freeze for up to one month. The thawed milk will be slightly grainy which is fine for baking but if you need it to be smooth for a sauce or curry, simply blend with a hand blender to re-emulsify the liquid.