Preheat the oven to 180°C/350°F. Grease a loaf pan with 1 teaspoon of oil and line it with a piece of parchment paper in the middle, with the excess hanging over the sides ( this makes it easier to remove the cake).
In a medium bowl, whisk together oil, mashed banana, eggs, coconut sugar, apple cider vinegar, and vanilla extract.
In a large bowl, combine the almond flour, flaxseed, cinnamon, baking soda, baking powder, and salt.
Mix dry ingredients with wet ones. Stir in the chocolate chips, if using.
Transfer to the prepared tin, smooth surface, and sprinkle with chocolate chips, if using, pressing gently onto the surface. Bake for 35-45 minutes or until golden and a toothpick inserted in the center comes out clean.
Cool in pan for 15 minutes, then transfer to a wire rack to cool completely.
Slice and serve.