Heat the oven to 180C (160C fan)/350F/gas mark 4, and line a 23 cm springform cake tin with baking paper, making sure there are no gaps for liquid to escape through later.
Using a food processor with a slicing disc, finely slice the apples into 2 mm-thick half-moons, then layer them horizontally in the cake tin, making sure there are no big gaps and pressing down each layer as you go.
Break the eggs into a large bowl, add the double cream and sugar, and whisk well.
Evenly sprinkle the baking powder and flour on top and whisk again.
Slowly pour this batter over the sliced apples, then give the tin a gentle shimmy so it falls into and fills any gaps in the apples, if need be.
Bake for an hour and 40 minutes (if need be, turn the tin around in the oven halfway through), until the cake is evenly golden brown on top and there are lots of browned apple slices showing through.
Remove from the oven, leave to cool to room temperature, then chill in the fridge for at least four hours, or overnight.
Unmould the cake from its tin, peel off the paper and place on a serving plate.
Slice with a sharp knife and serve with big spoonfuls of creme fraiche alongside.