Dough: In a mixing bowl add the butter, sugar and vanilla then beat until fluffy. Add the eggs individually and mix well after each addition. Beat in lemon zest with the last egg.
Add the flour and baking powder to the butter mix in seven additions. Stir quickly with an electric mixer on low speed after each addition. Don't over beat.
Peel the apples then quarter, core and cut into thin slices. Mix with lemon juice and cinnamon sugar then fold into the batter.
Preheat the oven to 200 degrees C. Line a baking tray with baking paper.
Spread the apple dough onto the prepared baking tray.
Topping: Spread a thin layer applesauce over the dough.
Streusel Topping: Dice the butter then combine with the sugar, vanilla, ground almonds and flour. Process with the dough hook to crumble (or crumble with your finger tips). Spread the crumble over the applesauce.