Preheat and prepare pan. Position a rack in the center of your oven. Preheat oven to 350oF (177°C). Spray a 9x5” loaf pan with non-stick cooking spray or line with parchment paper and set aside.
Mash bananas. In a small mixing bowl, mash bananas with a fork. Set aside. 1 ½ cups (340 g) very ripe bananas (about 4 medium)
Combine dry ingredients. In a mixing bowl, whisk together flour, baking soda, salt, and cinnamon. 2 ½ cups (300 g) all purpose flour 1 teaspoon baking soda 1 teaspoon salt ½ teaspoon ground cinnamon
Combine wet ingredients. Whisk together the sugar, melted butter, eggs, vanilla extract and buttermilk. Whisk to combine. 1 ¼ cups (250 g) granulated white sugar ½ cup (1 stick, 113 g) unsalted butter 2 large eggs ½ cup (120 ml) buttermilk 2 teaspoons vanilla extract
Combine mashed bananas, wet and dry ingredients. Add mashed bananas and the dry ingredients to the wet ingredients and mix together with a spatula until just combined. Do not overmix. Batter will be slightly lumpy.
Bake. Pour batter into prepared loaf pan and bake for 60-65 minutes until a toothpick inserted in the center of the bread comes out clean. (If baking in a glass pan, you may need to add on an additional 5 minutes of baking time). Remove from the oven and allow the bread to cool completely in the pan set on a wire cooling rack. Store the bread, and any leftovers, covered at room temperature for 2 days, or in the refrigerator for up to 1 week.