Pour the apple cider vinegar into a ¼ measuring cup. Fill the remaining cup with dairy free milk. Let set for 10 mins (this makes vegan buttermilk)
Preheat your oven to 375 degrees. Spray or grease a 4x8-inch loaf pan very well. In a large bowl, add the peeled bananas and using the back of a fork, mash them well. No large chunks should remain. Try to mash as much as possible.
To the bananas, add in the vegan buttermilk just made, melted butter, applesauce, and vanilla. Whisk together until smooth.
Mix in both of the sugars.
Add peanut butter and beat until the mixture is combined.
Scrape the bowl down and then sift in the flour, baking powder, baking soda, cinnamon and salt.
Fold just until combined.
Add to the bowl chopped walnuts or vegan chocolate chips if adding, and gently fold just until combined. Do not overmix.
Pour into greased bread pan and tap the bottom of the pan to ensure it's evenly leveled. Do not fill more than ⅔ full. *If you have too much batter, make mini muffins or similar with remaining batter after bread is done. Place in oven for 55-60 minutes on the center rack of the oven. When done, a toothpick inserted into the center comes out clean.
*The top of the bread should be a deep brown color. If after 45 minutes, your bread needs more time, cover the top with foil and continue cooking in 5 minute intervals until the toothpick comes out clean.
Remove from oven and place on a cool rack to cool completely before turning out.