Preheat the oven to 350°F (175°C) and grease an 8-inch springform pan.

In a bowl, combine 1 ½ cups flour, ½ cup brown sugar, ¼ cup granulated sugar, ½ teaspoon salt, 1 teaspoon ground cinnamon, and ¼ teaspoon nutmeg. Pour in the melted butter and vanilla, mixing until the mixture is evenly moistened and crumbly.

In a separate bowl, cream together 4 tablespoons of butter with ½ cup granulated sugar until fluffy. Add in the egg, vanilla, and sour cream, mixing well.

In another bowl, whisk together 1 cup flour, ¼ teaspoon baking soda, ¼ teaspoon salt, and ½ teaspoon baking powder; then gently fold this dry mixture into the butter mixture until just combined.

Spread half of the cake batter into the prepared pan. Next, sprinkle chopped apples evenly over the batter, followed by 1 cup of the crumb topping. Finish with the remaining cake batter and top with the rest of the crumb mixture.

Bake for 40-50 minutes, or until a toothpick inserted in the center comes out clean.

In a small bowl, mix the ½ cup powdered sugar with 2 tablespoons apple cider, stirring until smooth.

Drizzle the warm glaze over the cooled cake.