Step 1: Heat oven to 350°F (175°C). Grease an 8-inch square pan and line it with parchment, leaving a little overhang.

Step 2: In a large bowl, whisk flour, baking powder, baking soda, cinnamon, nutmeg, ground ginger, and salt.

Step 3: Add diced apple, applesauce, brown sugar, oil, egg, and vanilla. Fold until just combined and no dry flour remains. Fold in crystallized ginger if using.

Step 4: Scrape batter into the pan and spread evenly. Sprinkle granulated sugar over the top for a delicate crunchy crust.

Step 5: Bake 32–38 minutes, until the center is set and a toothpick comes out clean or with a few moist crumbs.

Step 6: Cool in the pan for 15 minutes, then lift onto a rack using the parchment. Cool before slicing for the neatest pieces.