This may be a hypoxylon species, a sac fungi. Apparently, when they are fresh they are this reddish colour, but turn black with age. I can't remember which tree snag this was on, but if a birch, this could be a birch hypoxylon.
Oh the Venus of Willendorf, one of the very first artwork that is found and shows a mother-godess (date the 24.000 to 22.000 years before Christ) Fantastic found ! BV