Preheat the oven to 180°C (350°F).
Butter the pan and line it with parchment paper.
Melt the butter and let it cool slightly.
Mix the yogurt with the vinegar (skip the vinegar if using buttermilk).
Mash the bananas with a fork until coarsely mashed.
Whisk the sugar and eggs just until pale; no need to double the volume.
Add the melted butter or oil and mix well.
Incorporate the yogurt, salt, cinnamon, and mashed bananas, mixing until smooth.
Add the sifted flour and baking powder, then mix gently without overworking the batter.
Fold in the chopped nuts using a spatula until evenly distributed.
Pour the batter into the pan and smooth the top.
If you want to decorate with banana, cut one banana lengthwise and place the two slices, cut side down, on top of the batter.
Bake for about 55 minutes, depending on your oven. Check for doneness by inserting a skewer into the banana bread, it should come out clean.
Remove from the pan and transfer to a wire rack to cool.
I hope you enjoy this easy recipe for the famous American banana bread and feel inspired to try it yourself.