- Preheat oven to 350F (175C). Grease and flour a 9x5 inch loaf pan. 
- In a large bowl, mash the bananas until smooth. 
- Stir in the oil, sugar, egg, and vanilla extract until well combined. 
- In a separate bowl, whisk together the flour, baking soda, salt, and cinnamon (if using). 
- Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Do not overmix. 
- Pour the batter into the prepared loaf pan. 
- Bake for 50-60 minutes, or until a wooden skewer inserted into the center comes out clean. 
- Let the bread cool in the pan for 10 minutes before transferring it to a wire rack to cool completely. 
- Optional Tips: 
- - For a richer flavor, substitute brown sugar for granulated sugar. 
- - Chopped nuts (walnuts or pecans) or chocolate chips can be added to the batter for extra texture and flavor. 
- - If the top of the bread is browning too quickly, tent it with foil during the last 15-20 minutes of baking. 
- - For a vegan version, substitute the egg with a flax egg (1 tablespoon flaxseed meal mixed with 3 tablespoons water, let sit for 5 minutes).