Pre-heat oven to 350° (180° celsius). Line an 8 inch (20 cm) cake pan with parchment paper. Scrunch up the paper and then wet and ring out, shake out excess water before placing in the cake pan, although a little moisture doesn't hurt.
FOR THE BASE
In a small bowl mix together the brown sugar and cinnamon, then add the softened butter and combine, spread on the bottom of the prepared cake pan.Place the sliced apples on top.
FOR THE CAKE
In a medium Bowl whisk together flour, baking powder and salt, set aside.
In a medium bowl beat together butter, sugar and vanilla. Add the egg and beat until light and fluffy, about 2 minutes. Add flour mixture alternately with milk. Beat to combine.
Spoon batter over apple slices and spread evenly. Bake for approximately 40-45 minutes or until toothpick come out clean. Let cool until warm. Serve with a scoop of ice cream if desired. Enjoy!