This one might be an example of a little personal bias seeping in since I’m a former catcher myself, but Tony Pena was probably the Red Sox best catcher in the 1990s until they acquired Jason Varitek in 1997. Pena was a veteran of ten major league seasons before signing with the Red Sox as a free agent after the 1989 season. He only spent four seasons in Boston, from 1990-1993, but made a strong impact.
He had one of his best seasons in 1990 when he led the American League in games played for a catcher with 143 and putouts and finished second in fielding percentage and assists. He had another fine defensive year in 1991 and won a Gold Glove.
He was also well-known for his unique crouch where he stuck one of his legs out and sat on the ground in what looked like a split. (This was imitated by my friends and me when we played Wiffle Ball and even Little League, much to the consternation of our coaches!).
Offensively Pena was decent in Boston, producing a .229 average while hitting 17 home runs and 161 RBI. However, he wasn’t valued for his bat as much as he was his defense behind the plate and for that, Pena was a valuable member of the Red Sox in the 1990s despite his short time in Boston.