Prep the pan and oven. Heat oven to 350°F (175°C). Grease a 9x5-inch loaf pan and line with a parchment sling for easy removal.
Mash the bananas. In a large bowl, mash the bananas with a fork until mostly smooth with a few small lumps.
Whisk in the wet ingredients. Add oil, eggs, brown sugar, and vanilla.
Whisk until glossy and well combined.
Combine the dry ingredients. Sprinkle flour, baking soda, salt, and cinnamon over the wet mixture. Gently fold with a spatula just until no dry streaks remain. Do not overmix.
Add mix-ins (optional). Fold in chocolate chips or nuts.
Keep it light so the batter stays airy.
Fill the pan. Pour the batter into the prepared loaf pan and smooth the top. For a pretty split, run a buttered knife down the center.
Bake. Bake 50–60 minutes, until the top is deep golden and a tester comes out with a few moist crumbs. If it’s browning too fast, tent loosely with foil for the last 10–15 minutes.
Cool for best texture. Let it cool in the pan 10–15 minutes, then lift out and cool on a rack at least 45 minutes before slicing.
Slice and enjoy. Use a serrated knife for neat slices.
Serve warm or at room temperature.