Preheat your oven to 350°F (175°C) and prepare a standard loaf pan lined with parchment paper.

In a large mixing bowl, peel and mash the very ripe bananas until smooth, leaving no large lumps.

In another bowl, cream together the softened unsalted butter and granulated sugar until light and fluffy.

Add the large eggs and vanilla extract to the creamed mixture and beat until well combined.

Gently fold in the mashed bananas and full-fat sour cream into the wet mixture until just combined.

In a separate bowl, whisk together the all-purpose flour, baking soda, and salt.

Gradually add the dry ingredient mix to the wet banana batter, stirring gently until just combined.

Pour the batter into the prepared loaf pan, smoothing the top for even baking.

Bake for 55-60 minutes, checking for doneness with a toothpick inserted into the center.

Once baked, cool in the pan for 10 minutes before transferring to a wire rack to cool completely.