Butter a 8" or 9" cake pan completely and flour it. Shaking out the excess flour. Preheat your oven to 350°F.

Cut two apples in half and then in ½" apple slices. Cut the other two in half and into ¼" slices.

Get started on the topping. Add the butter and ½" slices into a 12" skillet. Cook for about 4-6 minutes over medium-high heat. Add the ¼" apple slices, along with the brown sugar and lemon juice, stirring constantly. Only cook for about a minute more until the sugar dissolves and the apples are coated.

Take the pan off the heat and transfer the mixture into the prepared cake pan. Spread the apple mixture evenly. Press down slightly. Set aside.

Sift together the flour, baking powder, cinnamon, nutmeg and salt. Set aside.

Whisk together the eggs and sugars until thicker and slightly paler, about a minute.

Slowly pour in melted butter that's been cooled slightly. Whisk until combined. Add in the sour cream and vanilla and mix until fully combined.

Gently fold in the dry ingredients until just combined. Don't overmix.

Pour this batter on top of the apples in the pan and spread evenly until the apples don't show anymore.

Lightly tap the pan on top of a countertop. Bake for about 30-40 minutes at 350°F or until golden brown and a toothpick comes out with moist crumbs.

Let the pan cool on a wire rack for about 20 minutes.

Run a knife around the sides and use a wire rack to help flip the pan over. Make sure you do this over a baking sheet to catch any drippings.

Once flipped over, lift the pan off slowly. Let it cool for another 20 minutes before slicing and serving.