An apple crumble made recently by Humuhumu and me, with demarcations showing crumble layer (green) and apple layer (yellow).
This is the correct ratio of crumble to apple.
I have, on occasion, considered eliminating the fruit layer entirely and just making crumble crumble. That’s how much I like crumble. But it would probably be a little dry, so I’m willing to concede that it’s probably necessary to have some fruit.