Banana bread is at its best when it is just sweet enough--but not too sweet; its banana flavor rings clear and true--but is not overly aggressive; and you love it any time of day. It is remarkable how like a good friend banana bread can be.
Preheat the oven to 350 degrees F. Grease a 9-by-5-inch loaf pan with butter, then coat with flour, shaking off the excess.
Use an electric mixer to beat the brown sugar, granulated sugar and butter together until it is light and fluffy. Beat in the eggs; add the bananas, buttermilk and vanilla and beat until smooth. Stir in the cinnamon, flour, baking soda, baking powder and salt by hand with a rubber spatula. (You don’t want to over-beat the batter or the bread will be tough.) Stir in the pecans and coconut and pour into the prepared pan.
Bake until a toothpick inserted into the center of the bread comes out dry, about 1 hour 15 minutes. Allow to cool 5 minutes in the pan. Run a knife along the sides to loosen the loaf from the pan; invert to remove the bread and place it (bottom side down) on a wire rack to cool.