Preheat the oven to 350 degrees F. Spray three 9 x 5-inch bread loaf pans with cooking spray or line with paper liners. (This makes cleanup very easy)
In a large mixing bowl, using either a stand mixer or an electric hand mixer, cream the butter with the brown sugar and sugar. Add the bananas and incorporate.
Add the eggs, one at a time, incorporating well. Scrape the bottom and sides of the bowl with a rubber spatula occasionally.
Add vanilla extract and sour cream to the mixture and combine. Add the flour, baking soda, baking powder, and salt, stirring to combine. Once mixed thoroughly, fold in the pecans.
Divide the batter evenly into the prepared baking pans. Place the baking pans on a half sheet pan, lined with parchment paper. (This helps catch any dropped batter and helps easily rotate pans.)
Rotate your breads once through the baking process, so they bake evenly. Carefully rotate the entire half sheet pan 190 degrees about three quarters through the baking process. (Be very careful not to bump the pans or your bread will fall!!)
Bake for 50-60 minutes, or until a toothpick when inserted comes out mostly clean with a few moist crumbs.
Remove banana from the oven. Let cool in the baking pans for 10-15 minutes. Turn out of baking pans, place banana breads on a wire cooling rack to cool completely.
Once cooled, package into plastic bread bags with a twist tie.
Banana bread can be stored on the kitchen counter for several days. Refrigerate if super warm in the house. It can be frozen for 1-2 months.