Preheat your oven to 350°F (175°C). Grease and flour a 9x5 inch loaf pan, or line with parchment paper leaving an overhang on the long sides for easy removal.

In a large mixing bowl, whisk together the all-purpose flour, baking soda, salt, and granulated sugar. Set aside.

In a separate medium mixing bowl, mash the ripe bananas thoroughly with a fork or potato masher. Add the sour cream, melted butter, eggs, and vanilla extract to the mashed bananas. Whisk until well combined.

Pour the wet banana mixture into the dry flour mixture. Using a rubber spatula, gently fold the ingredients together until just combined. Be careful not to overmix; a few lumps are okay. Overmixing can lead to a tough banana bread.

Pour the batter into the prepared loaf pan and spread evenly. Bake for 55-65 minutes, or until a wooden skewer or toothpick inserted into the center comes out clean. If the top starts to brown too quickly, you can tent it loosely with aluminum foil.

Once baked, remove the loaf pan from the oven and let the banana bread cool in the pan for 10-15 minutes. This helps it firm up and prevents it from crumbling.

After cooling in the pan, carefully lift the banana bread out using the parchment paper overhang or invert it onto a wire rack to cool completely before slicing and serving.