Preheat oven to 350º F (180º C). Line a 9-inch springform pan pans with parchment paper. Lightly grease with baking spray with flour.
In a large bowl combine flour, baking powder, baking soda, apple pie spice, and salt.
In another bowl combine, brown sugar, maple syrup, butter, applesauce, buttermilk, and vanilla.
Add the flour mixture into the wet ingredients; mix just until combined. Fold in chopped apples.
Spread batter in prepared baking pan.
Prepare the Streusel (optional):
In a medium bowl combine flour, brown sugar, apple pie spice, and salt. Drizzle melted butter and vanilla. Toss with a fork to combine. Sprinkle the top of the cake with the streusel.
Bake for 25 – 30 minutes, or until a toothpick inserted in the center comes out clean. Let the cake cool in the pan on wire racks for 15 minutes before removing it from the pan. Allow the cake to cool completely.
FLOUR: I used white whole wheat flour in this recipe because I wanted a dense cake, but you can use half whole-wheat flour + half all-purpose flour or simply use just all-purpose flour. STORAGE: As this cake is moist, store it in a dry place at cool room temperature. If the weather is very hot or humid, you can store the cake in the refrigerator for up to 5 days. Wrap it well, so it doesn't absorb other odors. FREEZER: Let the cake cool completely. Then wrap it up in aluminum foil, then with plastic wrap. Place inside a large freezer Ziploc bag and freeze for up to 3 months.QUICK TIPS:
If you do not have apple pie spice, you can make your own by mixing together ½ teaspoon nutmeg, ½ teaspoon allspice, 1 teaspoon ground cinnamon.
Do not overmix the batter, or you'll end up with a dense cake.
Every oven is different, so baking times always have to be taken with a grain of salt. Oven thermostats can be wildly off, and that will all affect baking time, so keep an eye on yours. The cake(s) are done when a toothpick inserted in the center comes out clean.
Measure the ingredients correctly. I highly recommend using a kitchen scale to avoid using too much flour. This prevents you from ending up with a dense coffee cake.