Preheat oven to 350 degrees Fahrenheit.
Add the soy milk and vinegar, whisking together in a measuring cup. Let sit for 5-10 minutes until it slightly thickens.
Whisk the all-purpose flour, baking soda, salt, and cinnamon in a large mixing bowl.
In another large mixing bowl, whisk together the soy milk an vinegar mixture, maple syrup, egg, lemon zest, and vanilla extract. Then add the mashed banana, chia seeds, and the milk mixture. Combine until it forms a thick batter.
Then slowly pour the flour mixture into the banana mixture, and fold until all the flour has been mixed together with a spatula. Try not to overmix.
Grease a 9x3x5 inch loaf pan with some avocado oil or line with parchment paper. Pour in the batter and top with walnuts.
Bake for 45-50 minutes - then grab a toothpick and poke it in the center of the loaf. If it comes out clean without any batter, you can take it out of the oven. If the batter remains on the toothpick, you can bake it for another 5 minutes.
Remove from the oven and allow it to cool before slicing. Enjoy!