Preheat your oven to 350°F (175°C) and grease a 9-inch square baking pan.

Combine melted butter, brown sugar, eggs, and vanilla extract until smooth.

Mash the very ripe bananas in a separate bowl and stir into the wet mixture.

Whisk together flour, baking soda, and salt; then add to the wet mixture until just combined.

Fold in optional chopped pecans if using.

Pour the batter into the prepared pan and sprinkle granulated sugar on top.

Bake for 45-50 minutes and check for doneness with a toothpick.

Let the cake cool in the pan for 10-15 minutes before serving.