For the caramel: Open the can of pineapples and drain the juice into a saucepan. Save the pineapple slices for the cake.
To the saucepan with the pineapple juice, add the butter, the sugar, and the rum. Bring to a boil while stirring to melt the butter. Lower the heat and simmer for 5 minutes, or until the caramel has thickened. Remove from the heat.
For the cake: Preheat the oven to 350°F (175°C). Generously butter an 8-in (20 cm) square baking pan or a 9-in (23 cm) round baking pan. Pour the caramel into the pan and spread to an even layer.
Cut the pineapple slices into 4 to 6 pieces and set the pieces over the caramel in a single layer.
In a saucepan or in the microwave at a low heat setting, melt the Chocolats Favoris Dulce de Leche Chocolate Drops with the virgin coconut oil. Transfer to a mixing bowl, then whisk in the brown sugar, coconut milk, and eggs.
In a second large bowl, whisk together the flour, grated coconut, baking powder, baking soda, and salt. Fold the wet ingredients into the dry ingredients.
Pour the cake batter over the pineapple, using a spatula to spread it to an even layer. Bake for 30 to 35 minutes, or until the cake is golden brown and a toothpick inserted in the center of the cake comes out clean.
Let the cake rest on a wire rack for 5 to 10 minutes, then invert over a serving plate. (The cake may stick to the pan if it cools completely in it.) Transfer the pineapple pieces that stayed stuck in the pan, if any. Enjoy warm.