Preheat your oven to 350℉. Gather all of your ingredients, along with your loaf pan, mixing bowls, and utensils. *The 'spoon and sweep' method is the most accurate way to measure flour, aside from weighing it on a kitchen scale. Use your spoon to gently stir and fluff the flour in its container, then scoop the flour directly into the measuring cup, using the straight edge of the spoon to sweep away the excess flour once the cup is full.In a small sauté pan, lightly toast the walnuts (or pecans) over medium heat, just until they are warm. Using a paper towel, generously grease the bottom and sides of your loaf pan with the tablespoon of melted butter and set aside.
Into the large mixing bowl, stir together the flour, toasted nuts, granulated sugar, baking soda, cinnamon, salt and nutmeg. Set aside.
In a smaller mixing bowl, whisk together the eggs, sour cream, light brown sugar and vanilla extract until fully emulsified. The color and texture will look similar to a rich caramel.
Whisk the mashed bananas into the egg mixture and then fold into the dry ingredients, mixing until no dry ingredients remain.
Pour the batter into the prepared loaf pan and smooth out the top so the bread bakes evenly. Bake in your preheated oven for approximately 1 hour, or until a toothpick inserted into the center of the bread comes out clean.
Allow the bread to cool in the pan for about 15 minutes before attempting to remove it, to avoid sticking. Turn out the bread and allow to cool completely on a wire rack. After cooling completely, bread may be stored at room temperature for a few days if kept in a container with a tight-fitting lid, or, if preferred, wrapped tightly in plastic wrap and stored in the refrigerator.