Preheat oven to 350°F.
Prepare a 9-inch round cake by buttering the pan completely
Mix together flour, baking powder, baking soda, and salt in a medium bowl.
In the bowl of your mixer, beat the softened butter and brown sugar at medium to high speed until pale and fluffy.
Add the eggs one at a time, then add the rum.
Add cream of coconut and blend well, ( the batter may look curdled, don’t worry it will come together)
Add the dry ingredients, one third at a time, mixing and scraping down bowl between additions. Do not overmix, mix only long enough to incorporate the dry ingredients..
Spread batter evenly in the prepared pan. Bake until golden and a tooth pick or skewer inserted in center of cake comes out clean, 40 to 45 minutes.
Cool in pan on a wire rack 10 minutes, then run a knife around edge of pan to loosen and invert on your serving dish.*
For the frosting, in the bowl of your mixer, whip the cream cheese and mascarpone until light and fluffy.
Add the confectioners ’ sugar and salt then continue to mix until well blended
Add the cream of coconut, and vanilla whip at high speed until fully blended
Spread a liberal amount of frosting on the cooled cake and sprinkle the coconut over the top of the frosting as a garnish*