In a large mixing bowl, combine the mixed dried fruits and dark rum. Ensure that the fruits are fully submerged in the rum. Cover the bowl with aluminum foil and let it sit at room temperature for at least 24 hours, or up to 1 week, to allow the fruits to soak and absorb the flavors.
Preheat your oven to 325°F (160°C).In another large mixing bowl, cream together the softened butter and granulated sugar until light and fluffy.
Beat in the eggs, one at a time, ensuring each egg is fully incorporated before adding the next.In a separate bowl, sift together the all-purpose flour, baking powder, ground cinnamon, ground nutmeg, ground allspice, ground cloves, and salt.
Gradually add the dry ingredients to the creamed butter mixture, alternating with the molasses. Mix well after each addition.Fold in the soaked dried fruits, along with any remaining rum in the bowl. Stir until the fruits are evenly distributed throughout the batter.
Pour the batter into the greased and lined baking pan, smoothing the top with a spatula.Place the pan in the preheated oven and bake for 2-3 hours, or until a skewer or toothpick inserted into the center comes out clean. The baking time may vary, so keep a close eye on the cake.
Once baked, remove the cake from the oven and let it cool in the pan for 10 minutes. Then, transfer it to a cooling rack to cool completely.
While the cake is still warm, brush the top with additional rum for added moisture and flavor.
Once fully cooled, wrap the cake tightly in plastic wrap or aluminum foil and let it sit for at least 1 day or up to several weeks to allow the flavors to develop and meld together.
Slice and serve the Caribbean Black Cake as desired. It can be enjoyed on its own or with a dollop of whipped cream or a scoop of ice cream.