Preheat the oven to 350 degrees Fahrenheit.
Add the bananas to a large mixing bowl and use a potato masher or fork to mash them well.
Add the unsweetened milk, maple syrup, vanilla extract, salt, cinnamon, nutmeg, and apple cider vinegar, then mix well.
Add the melted coconut oil and mix again.
Add the buckwheat flour and baking soda and use a whisk to mix well.
Pour the batter into a medium sized loaf pan (mine is 9.25 x 5.25 x 2.75 inches) lined with parchment paper.
Bake for 38 minutes at 350 degrees Fahrenheit (or until a toothpick inserted into the center of the banana bread looks clean upon removal).
Let cool completely before removing from the pan and slicing.