Cover the mixing bowl with plastic wrap or a beeswax wrap to create an airtight seal to prevent batter from drying out. Allow the mixture to ferment at room temperature for 8-12 hours. This long fermentation enhances the bread's flavor and digestibility.

Preheat your oven to 350°F (175°C).

Mash your bananas very well until there are almost no lumps, this will help them incorporate easier into the fermented batter.

To the fermented mixture, add salt, baking soda, ground cinnamon, and vanilla extract.  Mix on low speed until the ingredients are combined. Slowly add in the mashed bananas a little bit at a time to allow them to incorporate easier. Once it seems to be incorporated well, use a silicone spatula to scrape the sides of the bowl and especially the bottom to make sure everything has bananas included.

If using, fold in the chopped walnuts with a spatula, ensuring they are evenly distributed throughout the batter.

Grease a 9x5-inch loaf pan or line it with parchment paper for easy removal.

Pour the batter into the prepared loaf pan, smoothing the top with a spatula. If desired, sprinkle coconut sugar or brown sugar over the surface for a sweet, caramelized crust.

Bake in the preheated oven for 50-60 minutes. To check for doneness, insert a toothpick into the center of the loaf; it should come out clean or with only a few moist crumbs attached.

Once baked, remove the bread from the oven and let it cool in the pan for about 10 minutes.

Transfer the loaf to a wire rack to cool completely before slicing. This cooling process ensures the bread sets properly, resulting in clean slices.