In a mixing bowl, cream together the butter and sugar until smooth and creamy.
After that, beat in the vanilla extract, followed by the eggs one at a time.
Combine the baking powder, flour, salt, and cinnamon in a separate mixing bowl.
Along with the milk, fold the dry ingredients into the wet components.
Once the butter has formed, pour it into the prepared pan and top with the sliced apples, ensuring that they are evenly distributed.
Spread the streusel topping evenly over the apples.
Preheat the oven to 350°F and bake for 75 minutes, or until golden brown and crunchy on top.
Remove from the heat and set aside to cool slightly before removing the cake from the tin.
Dust the cake with powdered sugar when ready to serve, slice, and enjoy!
Keep the cake at room temperature for up to 4 days in an airtight container.