Preheat oven to 175°C (~350°F).
Grease a 9x5-inch loaf pan or line it with parchment paper for easy removal.
In a large mixing bowl, mash the ripe bananas with a fork until smooth and creamy.
The riper the bananas, the sweeter and more aromatic your bread will be.
Add Greek yogurt, melted coconut oil (or butter), brown sugar (or honey), eggs, and vanilla extract to the mashed bananas.
Whisk until smooth and well combined.
In a separate bowl, whisk together flour, baking soda, salt, and cinnamon (if using).
Gradually add the dry mixture to the wet ingredients.
Stir gently until just combined — overmixing can make the bread dense.
Fold in the walnuts or chocolate chips, if desired.
Pour the batter into the prepared loaf pan.
Bake for 50–60 minutes, or until a toothpick inserted into the center comes out clean.
The top should be golden brown and slightly cracked.
Allow the banana bread to cool in the pan for 10 minutes, then transfer to a wire rack.
Slice and enjoy warm or at room temperature.