Preheat the oven to 425 °F (220 °C) and grease a 9" (23 cm) springform pan.
In a medium mixing bowl, stir together the flour, sugar, baking powder, and salt. Set aside.
1/2 cup (62 grams) white whole wheat flour, 1/3 cup (67 grams) raw sugar, 1 tablespoon baking powder, 1/8 teaspoon salt
In a large mixing bowl, stir together the eggs, coconut oil, milk, vanilla extract and lemon zest.
2 large eggs, 2 tablespoons refined coconut oil, 1/3 cup (80 ml) milk of choice, 1/2 teaspoon vanilla extract, 1 lemon
Add the dry mix to the wet and stir just until combined. Add the apples and coat them thoroughly in the batter.
2 pounds (907 grams or about 5 medium) apples
Pour into the greased pan and push down any apples that are sticking up (so that they don't burn).
Bake for 25-35 minutes. The time will depend on your apples. The top should be quite firm and golden.
Meanwhile, prepare the topping by combining all the topping ingredients in a small bowl.
1/3 cup (67 grams) raw sugar, 1 large egg, 1 tablespoon lemon zest, 3 tablespoons (42 grams) refined coconut oil, pinch salt
Remove the cake from the oven and pour the topping evenly over the top. Continue baking for another 10 minutes or until the top is a deep golden brown and feels firm.
Let the cake cool for 10 minutes and then run a knife around the edges of the pan. Remove the springform ring and let the cake cool for at least another 30 minutes. Can be served warm but I think the cake is best after having rested for several hours.
Store the cooled cake at room temperature for up to 1 day.