Preheat the oven to 350?F. Grease a 9 x 13-inch baking dish with 1/2 tablespoon butter.
Melt 3 tablespoons butter in a skillet. Add the pineapple, bananas, 1 teaspoon brown sugar, 1/4 teaspoon cinnamon, 1/4 teaspoon allspice, and 1/4 teaspoon nutmeg and cook until the fruit begins to soften, about 5 minutes.
Whisk the eggs in a large bowl. Whisk in the cream, coconut milk, remaining 1 1/4 cups brown sugar, vanilla, remaining 1 teaspoon cinnamon, 1/2 teaspoon allspice, and 1/4 teaspoon nutmeg. Add the bread and the fruit and stir well, then mix in the remaining 2 tablespoons melted butter. Pour into the prepared dish.
Bake until firm when pressed in the center, about 1 hour. Cool on a wire rack until just warm, about 20 minutes. Serve with warm Coconut Rum Sauce and garnish with the toasted coconut.
Makes 10 to 12 servings