• Preheat the oven to 350 ºF (175 °C). Butter and flour an 8-inch springform pan, lining the bottom with a circle of parchment. Set aside. Attach the beater attachments to the Braun MultiMix Hand Mixer to get it ready to use. 

Vanilla cake batter

• In a bowl, with the hand mixer, stir together the flour, baking powder, and salt. Set aside.
• In a large bowl, beat together the butter and the sugar until it is well mixed, light and fluffy. Mix in the vanilla, and then the eggs, one at a time. Be sure to move the mixer around the edges of the bowl to make sure the ingredients are well mixed.
• Alternate adding the flour mixture and the milk, beginning and ending with the flour. Stir just to combine on a lower speed.
• Transfer the vanilla cake batter to the prepared pan and smooth it out.

Apple filling

• In a bowl, combine the chopped apple with the lemon juice and the spices. Stir well then dollop the apple filling over the cake batter, spreading it into an even layer.

Crumble topping

• In a bowl using the electric mixer fitted with the beater attachments, cream together the butter, the sugar, and the salt. Make sure it is creamy and well mixed before adding the flour and oats. The crumble will have the texture of cookie dough.
• Using your fingers, crumble chunks of cookie dough over the apple layer so that it is completely covered.
• Bake the cake for about 1 hour 15 minutes or until a cake tester inserted into the middle comes out clean.
• Let the cake cool on a wire rack for 20 to 30 minutes before removing the springform ring. The cake should unmold quite cleanly. You may need to release the sides with the help of a thin knife.