Prehear your oven to 350°F. Grease a standard sized loaf pan and line it with parchment paper, if desired. Set aside.
In a large bowl, whisk together the mashed banana, melted butter, granulated sugar, eggs, and vanilla extract.
Add in the flour, baking soda, cream of tartar, salt, and cinnamon. Gently whisk all of the ingredients together until there are no more floury bits in your batter.
Pour the banana bread batter into the prepared pan. Bake for 48-52 minutes. The top should be lightly golden, and a toothpick should come out clean. Allow the bread to cool for about 30 minutes.
After at least 30 minutes, it's time to coat the bread in cinnamon sugar. Remove the bread from the pan. Mix together the granulated sugar and cinnamon and pour it onto a large plate or bowl. Lightly brush the entire loaf with the melted butter. Place the loaf onto the cinnamon mixture and roll into each side to cover, or use a spoon or your hands and sprinkle it over all of the sides of the loaf to cover it completely.
Allow the bread to finish cooling completely. Cut into slices and enjoy for 3 to 4 days!