cinnamon streusel banana bread

Directions:

1. Preheat oven to 350°F. Lightly coat a 9-by-5-inch loaf pan with cooking spray. Whisk mashed bananas, oil, 1/3 cup brown sugar, eggs and vanilla together in a medium bowl until smooth.
2. Whisk 1 cup whole-wheat flour, all-purpose flour, baking soda, salt and baking powder together in a large bowl until well combined. Make a well in the center of the flour mixture and add banana mixture; fold until just combined. Pour half of the batter (about 2 cups) into the prepared loaf pan, spreading into an even layer.
3. Whisk walnuts, melted butter, cinnamon and the remaining 2 1/2 tablespoons brown sugar and 2 tablespoons whole-wheat flour in a medium bowl until combined. Sprinkle the streusel in an even layer over the batter in the pan. Pour the remaining batter (about 2 cups) over the streusel; spread into an even layer, covering the streusel entirely.
4. Bake until a wooden pick inserted in the center comes out with a few moist crumbs, about 1 hour. (Cover with foil halfway through cook time to prevent overbrowning, as needed.)
5. Let cool in the pan on a wire rack for 15 minutes. Carefully remove from the pan and cool slightly on the rack, about 45 minutes. Slice and serve warm or at room temperature.