• Preheat the oven to 350 degrees F. Grease and flour one 8.5 x 4.5-inch loaf pans.

Make the Batter

• Melt the butter over medium heat just until it is melted. Don't let it get too hot. If it does get hot (it will pop and splatter) allow to cool until it is barely warm, but still liquid.
• Place the all-purpose flour, the whole wheat flour, baking soda, salt, cinnamon, and nutmeg in a medium-sized bowl and whisk to combine. Crack the eggs into a separate small bowl
• Mash the bananas in a large bowl. Depending on the degree of ripeness you may need to use an electric mixer to puree the bananas. Add the brown sugar and melted butter and mix on medium speed with a handheld mixer until it is increased in volume and lighter in color - 2 minutes.
• Add one egg and the vanilla and mix on medium speed just until the egg is incorporated. Add the second egg and mix in just until incorporated.
• Add 1/2 of the dry ingredients to the batter and mix on low speed until incorporated. Add all of the sour cream and mix on medium speed until well combined. Add the remaining dry ingredients and mix on low speed until combined. Scrape the sides and bottom of the bowl to ensure all the ingredients are thoroughly combined.

Bake the Banana Bread

• Pour the batter into the prepared pan and smooth the top and sprinkle with the turbinado sugar.
• Bake the bread for 60-65 minutes, rotating the pan after the first 30 minutes. The loaf should have a cracked top and a cake tester inserted in the center should come out clean. You can also check for doneness by checking the internal temperature with an instant-read thermometer. It is should read about 205 degrees F.
• Cool the loaf in the pan for 10 minutes and then invert it onto a cooling rack and allow to cool to room temperature. The bread can be sliced and served while still slightly warm

Storing the Banana Bread

• After the bread has cooled to room temperature temperature wrap it in plastic wrap. It can be stored at room temperature for up to 2 days, and in the refrigerator for up 5 days.
• The bread will begin to dry out as it sits on the counter and then in the refrigerator but it will still be fine to eat.