Preheat your oven to 350°F (175°C) and prepare a 9" x 5" loaf pan by greasing it with butter or non-stick spray.

In a large bowl, whisk together 2 cups of all-purpose flour, 1 teaspoon ground cinnamon, 1 teaspoon baking powder, 1/2 teaspoon baking soda, and 1/4 teaspoon salt.

In another bowl, beat together 1/2 cup softened unsalted butter, 1/2 cup light brown sugar, and 1/2 cup creamy peanut butter until fluffy. Add 2 large eggs one at a time and mix in 1 teaspoon vanilla extract.

Gradually add the dry mixture to the creamed mixture, alternating with 1/2 cup sour cream, mixing until just combined.

Fold in 3-4 mashed overripe bananas and any optional chopped nuts gently without over-mixing.

Pour batter into the loaf pan and bake for 50-55 minutes until golden brown and a toothpick comes out clean.

Allow the bread to cool in the pan for about 10 minutes before transferring it to a wire rack to cool completely.