No.9 seed Kontaveit ousted Vondrousova in Moscow on Sunday (AEDT) with a commanding 6-3 6-4 victory.
The Estonian had lost both of her previous two meetings with Vondrousova, but needed only an hour and 14 minutes to reach her fifth final this year.
Kontaveit struck 26 winners, with her backhand a potent weapon, and broke five times – three of those coming in the first set after she failed to hold in the first game of the match.
The 25-year-old Tallinn native has lost only two of her past 22 matches, while her winning run indoors now stands at nine.
Standing in the way of Kontaveit and a fourth title in 2021 is home hope Alexandrova, who advanced to her first WTA 500 final when Maria Sakkari retired because of dizziness.
Alexandrova was leading 4-1 in the opening set when the No.4 seed from Greece decided she was unable to continue.
There will be an unseeded champion at the Tenerife Open after Colombian Camila Osorio beat Camila Giorgi 6-4 7-5.
Ann Li will play in her second title-decider of the year courtesy of an emphatic 6-2 6-1 triumph over Alize Cornet.