Total Time: 1 hr. 25 min.
Yield: 12 bars
1 stick salted butter, melted and cooled, plus more for baking dish
1 cup all-purpose flour
1 tsp. ground cinnamon
1/2 tsp. baking powder
1/2 tsp. salt
1/4 tsp. baking soda
1 cup sugar
1 large egg
1/2 chopped walnuts
2 large firm, sweet apples (about 1 lb. total), peeled, cored, and cut into 1/2-inch cubes (approx. 2 3/4 cups)
1. Preheat oven to 350° with rack in center position. Generously butter a 9x11 baking dish.
2. Whisk together flour, cinnamon, baking powder, salt and baking soda in a medium bowl.
3. In a separate bowl, beat together butter, sugar and egg with a hand mixer until pale, about 2 minutes. Add walnuts and apples and stir by hand until combined. Add flour mixture and stir until combined, about 30 seconds more.
4. Spread batter in pan and bake until golden brown and slightly firm, about 40 minutes. Let cool on a wire rack for 30 minutes, then cut into 12 bars.
*Bars can be stored in an airtight container for up to 5 days.