Preheat the oven to 350°F. Line or grease a 9x5 inch loaf pan.
Toast nuts if using. Spread on a baking sheet and bake for 5 to 7 minutes until fragrant.
In a large bowl, beat butter, brown sugar, and granulated sugar until creamy.
Add eggs and vanilla. Beat until smooth.
Stir in mashed bananas.
In a separate bowl, combine flour, blended oats, baking soda, baking powder, salt, and spices.
Fold the dry ingredients into the wet mixture gently.
Stir in sour cream until just combined.
Fold in nuts or other add-ins if using.
Pour batter into prepared pan and smooth the top.
Bake for 55 to 65 minutes. A toothpick should come out clean or with moist crumbs.
Cool in the pan for 20 minutes before slicing.