Preheat oven to 350 F. Grease a baking dish or 9 inch skillet and set aside.
To make apple filling, place a skillet over medium heat with apple, lemon juice, and cinnamon and sauté for 7 to 8 minutes, or until apples break down and become syrupy. Remove from heat and set aside.
In a blender or food processor, blend applesauce, dates and coconut milk on high for 3 to 4 minutes, or until the dates are puréed.
Add eggs and coconut oil to the blender and blend for one more minute to combine.
In a large bowl, stir together coconut flour, tapioca starch, and baking powder. Pour the date mixture from the blender into the dry ingredients and stir well. Allowed to rest for a few minutes to thicken.
Pour the batter into the greased baking dish or skillet. Poor the syrupy apple mixture evenly on top and use a spoon to press it into the batter.
To make the crunchy topping, stir together all ingredients with a fork and spread evenly over the top of the coffee cake. Place additional sliced apples on top if desired.
Bake at 350 F for 35-40 minutes, or until a knife inserted comes out clean. Cool for at least 15 minutes before slicing and serving.