Preheat oven to 350 degrees. Prepare an 8 or 9 inch baking dish by rubbing it with a bit of coconut oil.
Layer most of the sliced apples on the bottom of the baking dish, saving a few apple slices for the top, if desired. Set aside.
In a small bowl, mix together almond flour, baking powder and salt. Set aside.
In a medium bowl, whisk together the coconut oil and maple syrup. Add the eggs, vanilla extract and lemon juice and whisk until well combined.
Add the dry ingredients to the wet and mix until just combined. Pour batter into baking dish, covering the sliced apples. Top with remaining sliced apples.
Bake for about 35 minutes, or until an inserted toothpick comes out clean. Let cool completely before cutting and eating.