One of the simplest recipes to make now that the apples are here in abundance is apple crumble. Custard to go with it is a little more labour intensive but still a great ketogenic treat.
Slice up the apples, I never bother to peel them, then load up your baking dish and sprinkle with some Fibersugar. For crumble measure 200g fiberflour, 50-75g fibersugar, 120g butter and mix all together until it looks like coarse bread crumbs. Cover the apples and bake for 45mins.
If you like custard and don't mind stirring for 10 minutes this is a great application for ultrafine fiberflour.
Beat 50g ultra-fine, 50g fibersugar with 3 egg yolks. Meanwhile have 300 ml milk heating up, add vanilla pods or paste as you like. Pour some of the hot milk into the egg mixture stirring well and gradually add all the milk. Return all of this to the saucepan and heat gently while continually stirring until it thickens just the way you like it.