Preheat your oven to 180°C and grease a 35 x 12cm rectangular tart tin well.
Sift the flour and baking powder into a bowl. Add the butter and rub in with your fingertips until the mixture resembles breadcrumbs. Stir in the light brown sugar, castor sugar, cinnamon, cloves and ginger.
Press half of the mixture into the base of the tin. Arrange the apple wedges over the base.
Combine the remaining flour mixture with the extra baking powder, vanilla extract, egg and milk. (No need to worry about lumps.) Pour the mixture over the apple.
Pop the tray in the oven and bake for an hour or until the filling is cooked through. Cool, then cut into slices.