In a large mixing bowl, combine the cornmeal, sugar, coconut milk, salt, and melted butter. Mix until all the ingredients are well combined.

Cut the banana leaves into rectangles and wipe them down with a damp cloth to remove any dirt or debris.

Take a scoop of the mixture and place it onto the banana leaf. Then, wrap the banana leaf around the mixture to form a small bundle. Tie the bundle with a string to keep it together.

Repeat the previous step until all the bundles are prepared.

Steam the bundles for 30 minutes until they are cooked through.

Remove the bundles from the steamer and let them cool for a few minutes.

Unwrap the banana leaves and serve the tamalitos or ducunu.