Adjust oven rack to lower middle position (so that top of pan will be in center of oven) and heat oven to 350 degrees. Grease bottom only of regular loaf pan, or grease and flour bottom and sides of nonstick 9-by-5-by-3-inch loaf pan. Set aside.

If using, spread nuts on rimmed baking sheet and bake until fragrant and deep golden brown, 5 to 10 minutes. Transfer nuts to cutting board to cool; chop coarsely and set aside.

Whisk the flour, baking soda, salt, and nuts together in a large bowl. Set aside.

In the bowl of an electric mixer, beat together the butter and sugar on medium speed until light and fluffy. Add the eggs one at a time, beating well after each addition. Add the bananas and beat until smooth. Add the buttermilk and vanilla and beat just until combined. Pour banana mixture onto dry ingredients and gently fold until just incorporated. The batter should be slightly lumpy.

Pour the batter into the prepared pan and smooth the top. It should be no more than two-thirds full. Bake until the loaf is golden brown, the edges pull away from the sides of the pan and a toothpick inserted in center comes out clean, about 1 hour and 15 minutes. Rotate the pan periodically to ensure even browning. Let the bread rest in the pan for 5 minutes, then turn the loaf out onto a wire rack and let cool completely. Cut into thick slices to serve.

Makes one 9-by-5-inch loaf.

Cooks Notes:

If using a glass 9-by-5-by-3-inch loaf pan, bake at 325 degrees F for about 1 1/2 hours. To make mini muffins, bake for about 18 to 20 minutes.