Step 1

Preheat oven to 350 degrees F. Generously spray bottom and sides of a 9x5-inch loaf pan with nonstick cooking spray.

Step 2

In a small bowl, stir together the chopped apple, 2 tablespoons brown sugar, and 2 teaspoons cinnamon. Set aside.

Step 3

In a medium bowl, whisk together white whole wheat flour, baking powder, baking soda, and salt.

Step 4

In the bowl of a stand mixer (or you can mix the batter by hand), combine the Greek yogurt, applesauce, and honey, eggs and vanilla. Beat on medium speed until combined. Scrape down the sides of the bowl with a rubber spatula. Reduce mixer speed to low and slowly mix in the melted butter.

Step 5

With the mixer still running on low, gradually incorporate the dry ingredients until barely combined, being careful not to over-mix. (The batter will be thick.) Use a rubber spatula to gently fold in the apples and any cinnamon-sugar left in the bowl. Transfer batter to the prepared loaf pan.

Step 6

In a medium bowl, stir together oats, white whole wheat flour, brown sugar, and cinnamon. Use your fingertips to work the cold butter into the oat mixture. Stir in the walnuts. Sprinkle the streusel over the batter in the pan and gently press it down with your hand.

Step 7

Bake bread for 55-65 minutes, until a tester inserted down into the loaf comes out with just a few moist crumbs attached. Check bread after 45 minutes and cover with foil as needed to prevent over-browning of the topping. Let bread cool in the pan on a wire rack for 15 minutes before carefully removing to the rack to cool completely before slicing and serving.