1/2 cup (1 stick) unsalted butter, room temperature, plus more for pan
1 medium apple, such as Gala or Fuji, peeled and diced small
3/4 cup pecans, toasted and coarsely chopped
2 and 1/2 cups all-purpose flour
2 teaspoons baking powder
1 teaspoon ground nutmeg
1/4 teaspoon salt
3/4 cup unsweetened applesauce
1/2 cup low-fat plain yogurt
1 and 1/3 cups granulated sugar
1 teaspoon packed finely grated orange zest
3 large eggs
confectioners' sugar, for dusting
Preheat oven to 350 degrees. Butter a 9-inch square baking pan. Line with parchment paper, leaving a 2-inch overhang on two sides. Butter parchment. In a medium bowl, toss apple and pecans with 2 tablespoons flour to coat. In another medium bowl, whisk together remaining flour, baking powder, nutmeg, and salt. In a small bowl, combine applesauce and yogurt.
In a large bowl, using an electric mixer, beat butter, granulated sugar, and orange zest on high until light and fluffy, 3 minutes, scraping down bowl as needed. Beat in eggs, one at a time, until combined. With mixer on low, add flour mixture in three additions, alternating with two additions applesauce mixture, and beat to combine. Fold in apples and pecans.
Transfer batter to pan and smooth top. Bake until golden and toothpick inserted in center comes out clean, about 50 minutes. Let cool in pan on wire rack, 20 minutes.
Using parchment, lift cake from pan.
Dust with confectioners' sugar before serving.