Preheat oven to 350 degrees. Grease a 4- by 8-inch loaf pan and line bottom and sides with parchment paper, with parchment hanging slightly over sides of pan.
In a small bowl, whisk together flour, baking soda, salt and pecans. In a medium bowl, mix the bananas, sour cream and vanilla extract.
In a bowl of an electric mixer on medium speed, beat butter until creamy. Add granulated sugar and brown sugar and beat until light and fluffy, about 2 to 3 minutes. Scrape down sides of bowl. Add eggs and mix until combined. Reduce speed to low, add flour mixture and mix until almost incorporated. Add banana mixture and mix until just combined. Scrape down sides of bowl and finish mixing with a spatula until batter is completely combined. Pour batter into prepared baking pan and bake until top is dark brown and a wooden skewer or toothpick inserted into the center comes out clean, about 45 to 55 minutes. Remove from oven, transfer pan to a wire rack and let cool for 20 minutes. Using parchment, lift loaf out of pan, peel off paper and let bread finish cooling on wire rack.
Nutrition information per each of 12 slices:
Calories270Fat14 gSodium320 mg
Carbohydrates35 gSaturated fat6 gTotal sugars20 mg