Preheat your oven to 350°F (175°C). This ensures that the banana bread bakes evenly and rises properly.

Grease a 9x5 inch loaf pan with butter or non-stick spray. This prevents the bread from sticking to the pan.

In a large mixing bowl, mash the ripe bananas with a fork until smooth. The riper the bananas, the sweeter the bread will be.

Add the softened butter and granulated sugar to the mashed bananas. Mix well until combined. This creates a creamy base for the bread.

Stir in the sour cream, eggs, and vanilla extract until fully incorporated. The sour cream adds moisture and a slight tang to the bread.

In a separate bowl, whisk together the sifted all-purpose flour, baking soda, and salt. This helps to evenly distribute the leavening agent and ensures a uniform texture.

Gradually add the dry ingredients to the wet mixture, folding gently with a spatula. Be careful not to overmix; this will keep the bread light and fluffy.

If using, fold in the chopped walnuts or pecans at this stage for added texture and flavor.

Pour the batter into the prepared loaf pan, smoothing the top with a spatula.

Bake in the preheated oven for 60-65 minutes, or until a toothpick inserted into the center comes out clean. This indicates that the bread is fully cooked.

Once baked, remove the loaf from the oven and let it cool in the pan for about 10 minutes before transferring it to a wire rack to cool completely.

Slice the banana bread once it has cooled. Serve plain or with a pat of butter for extra richness.