Charles Leclerc pushed Red Bull rival Sergio Perez off the top of the time sheets to end Friday practice for the Azerbaijan Grand Prix with the fastest time for Ferrari.
The Monegasque, who had trailed Perez at the end of the first session, pulled out a 1:43.224-second lap in the second hour of running to end the day 0.248 seconds clear of the Mexican.
Championship leader Max Verstappen was third 0.356 seconds off the pace.
The Dutchman leads Leclerc by nine points in the overall standings after seven of this season's 22 rounds.
Perez, winner in Monaco two weeks ago who is bidding to become the first repeat winner in Baku on Sunday, is third 15 points behind his Red Bull team mate.
Behind the top-three, Fernando Alonso went fourth quickest for Alpine ahead of compatriot Carlos Sainz who was fifth for Ferrari. The double world champion showed promising pace in both sessions, having been fifth quickest in the opening hour.
Frenchman Pierre Gasly ended the day sixth for AlphaTauri ahead of George Russell in the Mercedes and team mate Yuki Tsunoda.
Esteban Ocon in the other Alpine and McLaren's Lando Norris rounded out the top-10 ahead of Aston Martin's Sebastian Vettel and seven-time world champion Lewis Hamilton.
The Azerbaijan Grand Prix, run around an unforgiving layout known for catching drivers out, has a reputation for serving up the unpredictable.
But there were no major incidents that disrupted running on Friday.
Mick Schumacher and Nicholas Latifi caused two virtual safety car periods during the first session. Several drivers also kissed the barriers or ran wide into the run-off areas as they tested the limits of the track.
Cars were also seen to be 'porpoising' or bouncing dramatically as they sped down the start-finish straight.