Preheat the oven to 350℉. Grease an 8" round cake pan with 3" high sides. Cut a round piece of parchment paper and line the bottom of the pan. Set aside.

In a large bowl, toss the apples with the lemon juice to prevent browning. Set aside.

In a small bowl, stir together the flour, baking powder, and salt. Set aside.

In another large bowl, whisk together the sugar, melted butter, oil, eggs, and vanilla. Using a whisk, mix the flour mixture into the egg sugar batter. Slowly stir in the milk and keep stirring until the batter is well blended. There may be small clumps of flour, but that's okay.

Pour 1/2 the batter into the prepared cake pan. Arrange half the apples on top of the batter and fit them so they are snug and overlapping. Gently spoon the remaining 1/2 of the batter on top of the apples. Then top the batter with the remaining apples, making sure to overlap them in a pretty pattern.

In a small bowl, stir together the brown sugar and cinnamon. Sprinkle over the apples on top of the cake. then sprinkle the sliced almonds on top of the sugar. (optional). Bake for 60-70 minutes or until a toothpick inserted into the center comes out clean or with just a few crumbs but no batter.

Remove the cake from the oven and cool on a baking rack for 10 minutes. Then use a knife to loosen the cake's edges away from the pan. Keep running the knife around the circumference until the cake is free from the pan's sides. Place a plate on top of the cake and invert. Remove the pan and then the parchment paper from the bottom side of the cake and turn the cake over onto the baking rack and let the cake cool completely. Serve with confectioner's sugar, whipped cream, or ice cream.