Remove and grease your slow cooker bowl.
Pour the flour, coconut and sugar into a large bowl.
140 g self raising flour, 50 g desiccated coconut, 100 g golden caster sugar
Mix together the butter, milk and egg in a jug, and beat together well. Add the lime zest and juice.
80 g melted butter, 60 ml milk, 1 egg, zest of 2 limes and juice of 1 lime
Pour the jug contents onto the dry ingredients and mix well.
Pour the cake batter into your slow cooker bowl.
Mix together the sugar and lime juice for the sauce, then add the boiling water and mix again.
250 ml boiling water, 50 g golden caster sugar, juice of 1 lime
Pour the sauce ingredients over the cake batter in the bowl. It will look very strange but the sauce will end up underneath the sponge as it becomes firm.
Turn your slow cooker onto high and cook for around two hours, until the sponge is firm.
Serve warm!