I’m not sure whether this is the hoof fungus, Fomes fomentarius, or a Ganoderma bracket fungus. It was growing on a softwood deciduous tree, probably birch, at Dubbs Moss Cumbria Wildlife Trust nature reserve, southwest of Cockermouth.
Hoof fungus, also known as tinder fungus, was once considered to be mainly confined to the Scottish Highlands but it is spreading south.
iPad drawing using Clip Studio Paint.