2 cups (10 ounces) unbleached all-purpose flour, plus more for dusting the pan
1 1/4 cups walnuts, chopped coarse
3/4 cup (5 1/4 ounces) sugar
3/4 teaspoon baking soda
1/2 teaspoon salt
3 very ripe, soft, darkly speckled large bananas, mashed well (about 1 1/2 cups)
1/4 cup plain yogurt
2 large eggs, beaten lightly
6 tablespoons (3/4 stick) unsalted butter, melted and cooled
1 teaspoon vanilla extract
1. Adjust an oven rack to the lower-middle position and heat the oven to 350 degrees. Grease the bottom and sides of a 9 by 5-inch loaf pan; dust with flour, tapping out the excess.
2. Spread the walnuts on a baking sheet and toast until fragrant, 5 to 10 minutes. Set aside to cool.
3. Whisk the flour, sugar, baking soda, salt, and walnuts together in a large bowl; set aside.
4. Mix the mashed bananas, yogurt, eggs, butter, and vanilla with a wooden spoon in a medium bowl. Lightly fold the banana mixture into the dry ingredients with a rubber spatula until just combined and the batter looks thick and chunky. Scrape the batter into the prepared loaf pan.
5. Bake until the loaf is golden brown and a toothpick inserted in the center comes out clean, about 55 minutes. Cool in the pan for 5 minutes, then transfer to a wire rack. Serve warm or at room temperature. (The bread can be wrapped with plastic wrap and stored at room temperature for up to 3 days).