Preheat oven to 180 C. Grease and flour a 25cm ring cake tin. Mix flour, baking powder and salt together and set aside.
Sift flour, salt and baking powder together into a bowl.
In a large bowl, cream butter and sugar until light and fluffy. Add eggs one at a time; beat well. Mix in vanilla. Add flour mixture alternately with buttermilk, mixing well with each addition. Fold in coconut. Pour batter into prepared tin.
Rub in the butter until mixture looks like fine breadcrumbs. Add sugar, coconut and lime zest. Beat egg and add most of the milk and vanilla.
Bake in the preheated oven for 1 hour or until a skewer inserted into the cake comes out clean.
Make a well in centre of flour mixture. Add liquid and mix well to form a stiff cosistency, adding more milk if necessary.
Place in a greased 15cm (6 inch) cake tin and bake at 180 C /gas mark 4 for 40 minutes, or until a knife inserted in the middle comes out clean.