Preheat the oven to 350 F (170 C). Line a 9x5 loaf pan with parchment paper, leaving a bit of overhang on two sides.
In a small bowl mash about 2- 3 medium bananas to measure 1 cup mashed banana. Peel, core and dice the apples. Toss the peeled, cored and diced apples with 1 tablespoon of flour. Set aside for a moment. In a large bowl, whisk the flour, baking soda, cinnamon and salt together until well combined.
2 cups (240 g) all purpose flour, 1 teaspoon ground cinnamon , ¾ teaspoon baking soda , ½ teaspoon salt
In another large mixing bowl, melt the butter and cool for 5 - 10 minutes to room temperature. Whisk the light brown and granulated sugars, mashed banana, eggs, sour cream and vanilla extract into the cooled melted butter until smooth and well combined. Stir the dry ingredients into the wet until just combined. Stir in the diced apples. If you would like, stir in ½ cup chopped pecan or walnuts. ½ cup (113 g) unsalted butter, melted and cooled , ½ cup (100 g) light brown sugar , ½ cup (100 g) granulated sugar, 2 large eggs, room temperature, 1 cup mashed bananas , ¼ cup (60 g) sour cream, room temperature, 2 teaspoons (10 ml) vanilla extract , 1 cup peeled, cored and diced apples , ½ cup chopped walnuts or pecans, optional
Evenly pour the banana apple bread batter into the prepared pan. Top with a sprinkle of sugar if you like.Bake the apple banana bread for 55 - 65 minutes or until a toothpick inserted into the center of the bread comes out with a few moist (not wet or gummy) crumbs. Cool the banana apple bread in the loaf pan for 15 minutes. Use the parchment sling to lift the bread out of the pan. Fully cool the banana apple loaf for at least an hour at room temperature, slice and enjoy.