Preheat your oven to 350°F (175°C). Grease a loaf pan.
In a mixing bowl, combine mashed bananas, sugar, melted butter, and beaten egg.
In another bowl, whisk together flour, baking soda, and salt.
Gradually add the dry ingredients to the banana mixture, stirring until just combined.
Fold in the yogurt until the batter is smooth.
Pour the batter into the prepared loaf pan.
Bake for 50 minutes, or until a toothpick inserted into the center comes out clean.
Let the bread cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.