Preheat your oven to 350°F (175°C) and grease a 9-inch springform pan. Line the bottom with parchment paper for easy removal.
Peel, core, and dice the apples into 1/2-inch cubes. Toss them in a bowl with lemon juice, sugar, cinnamon, and nutmeg.
In a medium bowl, combine flour, brown sugar, cinnamon, and salt for the crumb topping. Add the cold cubed butter and use a pastry cutter or your fingertips to work it into the dry ingredients until you achieve pea-sized crumbs. Mix in the chopped pecans.
Whisk together the dry ingredients (flour, sugars, baking powder, baking soda, salt, cinnamon, and nutmeg) in a large bowl.
In a separate bowl, combine the wet ingredients (melted butter, eggs, sour cream, and vanilla).
Fold the wet ingredients into the dry ingredients until just combined - avoid overmixing.
Pour the batter into the prepared pan, spreading it evenly. Arrange the apple filling over the batter, gently pressing some pieces slightly into the batter.
Sprinkle the crumb topping evenly over the apples, covering the entire surface.
Bake for 50-55 minutes, or until a toothpick inserted into the center comes out clean. The internal temperature should reach 205°F for optimal doneness.
Allow the cake to cool in the pan for 15-20 minutes before removing the springform ring. Transfer to a wire rack to cool completely or serve slightly warm.