Preheat your oven to 325°F (163°C) and grease and flour two 8x4" loaf pans.

In a large bowl, cream together the butter and granulated sugar until light and fluffy, about 3-5 minutes.

Mash overripe bananas and whisk in the eggs and vanilla extract in another bowl.

Gently add the banana mixture to the creamed butter and sugar, stirring until just combined.

Sift together flour, baking soda, and salt in a separate bowl, then gradually fold into the wet mixture.

Incorporate the sour cream alternately with the dry ingredients until smoothly combined.

Divide the batter between the two prepared pans, smoothing the tops.

Bake for 50-60 minutes, checking doneness with a toothpick inserted into the center.

Allow the bread to cool in the pans for about 10 minutes before turning out onto a wire rack to cool completely.