Preheat oven to 350℉. Grease and line the bottom of an 8-inch round cake pan with parchment paper.
In a medium-sized bowl, whisk together the 2 ½ cups almond flour, 1 teaspoon baking powder, and ¼ teaspoon fine sea salt.
In a large bowl, whisk together the 4 large eggs, ¾ cup granulated sugar, and ¼ cup melted coconut oil.
Gently fold the dry ingredients into the wet ingredients and stir to form a smooth batter.
Pour the batter into the prepared pan and use a rubber spatula to spread it out evenly. Take the sliced, 2 medium apples and fan them out in a decorative pattern over the top.
Place in the oven and bake for 40-45 minutes, until the top is set and a toothpick inserted into the middle comes out clean. Cool in the pan set on a wire rack for 15 minutes, then gently remove and place on the rack to cool to room temperature.
Notes
Use fine almond flour. Fine-ground almond flour gives this cake its smooth, tender crumb. Almond meal will produce a more rustic, slightly coarser texture. So, if you prefer more texture, feel free to use almond meal!
Slice the apples thinly. Cutting the apples thinly does double duty - they will soften nicely during baking plus make it easier to create that pretty, fanned-out topping. I peeled my apples, but for a more rustic look you can leave them unpeeled.
Cool completely before slicing. The cake is quite tender when warm, like most gluten-free bakes, but will set and firm up as it cools. Use a serrated knife to cut slices.
A little cinnamon goes a long way. I love the warmth of a sprinkle of cinnamon, but the cake is just as lovely without it. A pinch of nutmeg or ground ginger would also be delicious, or try a combination.