Method

1. Preheat oven to 350F/175°C. Butter 1 (9- by 5- by 3-inch) metal loaf pan, then dust with flour, knocking out excess.
2. Sift together the flour, baking soda, cinnamon, and salt into a bowl.
3. Beat together eggs and sugar in bowl of electric mixer at medium-high speed until very thick and pale and mixture forms a ribbon when beater is lifted, about 10 minutes. Reduce speed to low and add oil in a slow stream, mixing, then mix in bananas, yogurt, and vanilla. Remove bowl from mixer and fold in flour mixture and walnuts gently but thoroughly.
4. Pour the batter into the loaf pan, spreading evenly, and bake in middle of oven until golden brown and a wooden pick or skewer comes out clean, 1 to 1 1/4 hours.
5. Cool loaf in pan on a rack 10 minutes, then turn out onto rack. Turn loaf right side up and cool completely.