Preheat: Heat the oven to 375°F (190°C). Line the bottom of a 10-inch springform pan with parchment paper and grease the sides.
Prep apples: Peel, core, and cut the apples into small cubes.
Cream: Beat the soft butter and sugar for 2 to 3 minutes until pale and fluffy.
Add eggs: Add the eggs one at a time, mixing well after each.
Dry ingredients: Add the vanilla pudding powder, flour, and baking powder. Mix on low just until combined.
Milk and apples: Mix in the milk until the batter is smooth and thick. Fold in the apple cubes.
Fill: Spread the batter evenly in the pan.
Top: Sprinkle cinnamon over the top, then scatter the sliced almonds.
Bake: Bake at 375°F (190°C) for 20 minutes.
Lower heat: Reduce to 350°F (175°C) and bake 20 more minutes, until golden and a toothpick comes out clean.
Cool: Cool in the pan for 15 minutes, then remove the springform ring.