Preheat oven to 350 degrees. Grease and flour a 9" cake pan.
for the crumble
In a medium bowl combine the butter, sugar, cinnamon, flour and salt and using the tines of a fork cream the mixture together. Add the oatmeal and coconut and work them into the crumble mixture until well combined.
for the batter
In a large bowl beat together the sugar and butter. Add the egg and beat until smooth. Add the extracts, baking powder and one cup of all purpose flour and beat until just combined. Beat in the buttermilk and cream of coconut. Add the remaining flour and beat until just incorporated.
Spread half of the batter evenly in the prepared pan and sprinkle one cup of the pineapple bits over the batter.
Stir the remaining pineapple into the other half of the batter. Drop by teaspoonfuls over the pineapple, leaving some spots uncovered by the batter. Sprinkle the crumble topping.
Bake for 55-60 minutes until a cake tester comes out clean. Cool to room temperature and turn out the buckle onto a serving plate.