- 1 stick salted butter, melted and cooled, plus more for dish
- 1 cup all-purpose flour
- 1 teaspoon ground cinnamon
- 1/2 teaspoon baking powder
- 1/2 teaspoon salt
- 1/4 teaspoon baking soda
- 1 cup sugar
- 1 large egg
- 1/2 cup chopped walnuts
- 2 large firm-sweet apples (about 1 pound total), peeled, cored, and cut into 1/2-inch cubes (2 3/4 cups)
- Preheat oven to 350 degrees with rack in center position. Generously butter an 8-by-11-inch baking dish.
- Whisk together flour, cinnamon, baking powder, salt, and baking soda in a medium bowl. In a separate bowl, beat together butter, sugar, and egg with a 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.
- Spread batter in pan, and bake until golden brown and slightly firm, about 40 minutes. Let cool on a wire rack 30 minutes, then cut into 12 bars.