Preheat the oven to 350℉.
Into a bowl, sift flour, then add baking powder and soda, and salt. Set aside.
Into another bowl, add sugar, brown sugar, egg, milk, sour cream, oil and vanilla extract. Whisk vigorously until well combined. Add in the dry ingredients and using a spatula fold the flour until combined. Do not over mix.
Melt the butter. Peel the apples and cut into wedges about an inch thick.
Place the apple wedges into a bowl and squeeze lemon juice over them and toss to coat. Add cinnamon and nutmeg and toss to coat. Set aside.
Prepare a 9 inch round pan by spraying it with baking nonstick spray. Then placing a round piece of parchment paper on the bottom to prevent the topping from sticking.
Pour the melted butter into the bottom of the pan. Sprinkle with brown sugar evenly. Add the seasoned apples in a circular pattern. Pour the batter over the apples and use a spatula to spread evenly.
Bake on the middle rack at 350℉ for 1 hour 10 mins. The cake should feel slightly firm in the middle. If it stills feels slightly mushy let it bake a few more mins. Even if a knife comes out clean, it may still not be cooked in the middle. So the firmness check is better. **If the top of the cake is getting too dark, cover it with aluminum foil.
Let it cool for 15 mins. Use a pairing knife to loosen any cake that has stuck to the sides. Place a plate on top and flip the cake over. Slowly pull the pan straight up and reveal the beautiful caramelized top!