Preheat the oven to 350°F (175°C) and grease a 9-inch round cake pan.
In a medium bowl, mix flour, baking powder, baking soda, cinnamon, nutmeg, and salt.
In a large bowl, whisk together the coconut sugar, oil, and vanilla.
Add applesauce and stir to combine.
Gradually add the dry ingredients to the wet, mixing until combined.
Fold in the chopped apple.
Pour the batter into the prepared pan, smoothing the top.
For the topping: Mix brown sugar and cinnamon and sprinkle over the cake.
Bake for 35-40 minutes or until a toothpick comes out clean.
Let cool for 10 minutes, then transfer to a wire rack to cool completely.