In an Uncanny X-men comic, 256ish (1990)... Back when Jim Lee was just beginning and Claremont was really on form... It's 1942 when Captain America meets Wolverine in Mandipoor while fighting Ninja's to see who can be in control of a 6 year old Kung-fu prodigy named Natasha Romanov.
She called Wolverine "Uncle Logan" from time to time but I wonder if there was some transitional period ever where she had to phase out the name "Uncle Steve"?
Natasha either had some Russian version of Nick Fury's Infinity Formula, or like her boyfriend "Bucky" she might have spent decades in suspended animation while she wasn't in use by the state... But as far as the comics are concerned, the Black Widow was conceived in the 1930s.
(Spider-Woman too, but that's a completely stranger story indeed.)