Preheat the oven to 190C/375F degrees. Lightly grease 8 muffin cups or line them with paper liners.
Thinly cut the starfruit to 8 slices. Gently remove the seeds from the fruit with a knife or spoon.
In a bowl, whisk the butter and monk fruit sweetener together until light and fluffy.
Add the eggs, one at a time and continue to whisk.
Add the coconut flour, coconut milk, baking powder, nutmeg, salt and cinnamon and whisk until the mixture is smooth. If the batter is too thick add additional coconut milk.
Spoon the batter into the prepared muffin pans.
Place a star fruit slice on the top of the muffin mixture.
Bake for 25-30 minutes until the muffins are firm.
Allow the muffins to cool in the pan for five minutes and transfer to a wire rack to cool completely.