In a saucepan, combine the coconut milk with the sugar and salt. Bring to a full boil and cook for about 6 minutes, stirring occasionally. In a bowl, combine the cornstarch with ¾ cup of water and, with a whisk, mix well into a slurry. Immediately pour the slurry into the saucepan and cook, continuously whisking until the mixture thickens into a pudding, about 2 minutes. Remove from the heat.
Pour the mixture through a colander. Transfer the strained pudding into a nonstick 12″x6″ deep dish or into individual martini glasses. Smooth out the surface, and set aside to cool. Refrigerate to completely set, about 2 hours. Dust with ground cinnamon, slice, and serve.