Preheat the oven to 325F. Line a 9x13x2-inch baking dish with a doubled dish towel.

Heat 3/4 cup of the sugar in a small, heavy-bottomed saucepan over low heat, stirring often, until the sugar has melted and caramelized to golden brown, about 5 minutes. Pour the caramel into a 9×5-inch loaf pan. Tilt the pan to cover the bottom and part of the sides with the caramel. Set aside.

Combine the banana, the remaining 3/4 cup sugar (1/2 cup if using sweetened coconut), the shredded coconut, nutmeg and salt in a bowl of an electric mixer and beat until smooth. Beat in the eggs until well mixed. Gradually beat in the coconut milk and then the evaporated milk. Beat in the vanilla and beat until the custard is well mixed.

Pour the custard into the prepared loaf pan. Set the pan in the baking dish and then put the dish into the preheated oven. Use a cup to add hot tap water to almost fill the baking dish. Bake until a toothpick inserted in the center comes out clean and the top is a light brown color, about 1 hour 15 minutes.

Remove the loaf pan from baking dish and set it on a wire rack to cool. (Let the water in the baking dish cool before removing it from the oven.) Refrigerate the custard for at least 5 hours.

To serve, set the loaf pan over direct heat until the bottom gets hot, about 1 minute. (This is to melt the caramel so the flan will unmold.) Run a knife around the edges to loosen the flan. Invert a serving dish on top of the loaf pan and then turn the mold upside down onto the plate. Remove the pan. Cut into slices and serve.