Ingredients

• 1/2 cup butter (1 stick), softened
  
• 1/2 cup packed brown sugar
  
• 1/2 cup granulated sugar
  
• 2 large eggs
  
• 2 teaspoons vanilla extract
  
• 1 cup mashed ripe banana (about 9 oz, roughly 2 1/2 medium bananas)
  
• 1 cup all-purpose flour, spooned and leveled
  
• 1/2 cup old-fashioned oats, blended into a powder
  
• 1 teaspoon baking soda
  
• 1 1/2 teaspoons baking powder
  
• 3/4 teaspoon kosher salt
  
• 1/2 cup sour cream
  
• 1/4 teaspoon cinnamon (optional)
  
• 1/8 teaspoon nutmeg (optional)
  
• 1/8 teaspoon cloves (optional)
  
• 1/2–3/4 cup toasted pecans or walnuts (optional)

Instructions

1. Prepare the pan:
   Heat the oven to 350°F. Coat a 9×5-inch loaf pan with nonstick spray or line it with parchment for easy removal.
2. Toast the nuts (if using):
   Spread 1/2–3/4 cup chopped walnuts or pecans on a baking sheet. Bake for 5–7 minutes, stirring every couple of minutes, until fragrant. Set aside to cool.
3. Cream the butter and sugars:
   In a large mixing bowl or stand mixer, beat the softened butter until smooth. Add both sugars and mix for about 2 minutes until light and fluffy, pausing to scrape the bowl.
4. Add eggs and vanilla:
   Mix in the eggs and vanilla extract, blending well and scraping the sides as needed.
5. Mash the bananas:
   Mash about 2 1/2 very ripe bananas with a fork or potato masher until you have about 1 cup of puree. Stir the mashed banana into the butter mixture.
6. Add the dry ingredients (but don’t mix yet):
   Add the 1 cup of flour to the bowl.
   Blend the oats in a food processor until powdered, then add that to the bowl as well.
   Sprinkle the baking soda, baking powder, and salt across the surface of the flour so they mix evenly.
   If you’re adding spices, stir in the cinnamon, nutmeg, and cloves now.
7. Combine the batter:
   Stir the dry ingredients into the wet mixture just until everything comes together. Scrape the sides and bottom well.
8. Add sour cream:
   Gently fold in the sour cream until fully incorporated.
9. Add nuts:
   Fold in the cooled toasted nuts if using.
10. Bake:
    Pour the batter into the prepared pan and smooth the surface.
    Bake for 55–65 minutes. Check doneness by inserting a toothpick deep into the center crack—no wet batter should cling to it. Moist crumbs are fine. The loaf should be deeply golden and slightly pulling away from the edges.
11. Cool:
    Let the bread cool on a rack for at least 20 minutes before slicing (or longer if you can resist).

• Keep covered at room temperature for up to 2 days.
  
• Refrigerate after that if any remains.
  
• For freezing: wrap the whole loaf in foil and then in a sealed bag, or freeze individual slices. Thaw inside the sealed packaging, then toast if desired.

• You can use up to 2 cups (18 oz) of mashed bananas without changing anything else, but the loaf will be denser.
  
• If you don’t want to use oats, substitute 1/2 cup all-purpose flour.
  
• A true 9×5-inch pan prevents overflow—smaller pans may cause spillover.