Preheat your oven to 350°F (175°C). Lightly grease a 9×5-inch loaf pan or line it with parchment paper.

In a large mixing bowl, cream the softened butter and sugar together until light and fluffy.

Beat in the eggs one at a time, mixing well after each addition.

In a separate bowl, whisk together the flour, baking soda, and salt.

Gradually add the dry ingredients to the wet mixture, stirring until just combined.

Fold in the mashed bananas, sour cream (or yogurt), vanilla extract, and cinnamon (if using). Stir until well incorporated.

Gently fold in the chopped nuts if desired.

Pour the batter into the prepared loaf pan and smooth the top.

Bake for 55 to 65 minutes, or until a toothpick inserted into the center comes out clean.

Let the banana bread cool in the pan for 10 minutes, then remove and transfer to a wire rack to cool completely.

Slice and serve warm, or store in an airtight container for up to 4 days.