- Preheat the oven to 350°F.Line a loaf pan with parchment paper or spray with cooking spray. 
- In a medium bowl, combine the coconut milk and vinegar. Whisk and set aside.  
- In a large bowl or stand mixer, combine buckwheat flour, cinnamon, baking powder, baking soda, and salt. Stir until blended.  
- To the bowl with the coconut milk and vinegar, mash in the banana, and add the vanilla extract. Whisk until creamy. You can also blend these ingredients together in a blender.  
- Pour the wet ingredients into the bowl with the flour mixture and beat until a batter is formed. Fold in the walnuts. Transfer the batter to the loaf pan.  
- Bake for 40 minutes. Remove the pan from the oven to turn, covering with a piece of foil to prevent burning on the top. Bake for another 10-15 minutes until toothpick comes out clean or internal temperature is at least 180 degrees. Allow the bread to completely cool in the pan, about 1-2 hours.