The victory puts Arsène Wenger's men in a strong position for the return leg on 12 April in Moscow.
"It was a spectacular first-half played at a high pace," cooed Wenger after the rout at the Emirates Stadium. "But it was an uncomfortable half as well for me because CSKA looked dangerous. That will help us to focus completely in the second game and not go there thinking it is job done."
Languishing in sixth place in the Premier League, 13 points adrift of the positions which lead to participation in next season's Uefa Champions League, Arsenal's last realistic hope of qualifying for that competition lie in winning the Europa League final in Lyon on 16 May.
That air of urgency was underlined in a pulsating 45 minutes.
Ramsey opened the scoring after nine minutes. The Wales international midfielder rounded off a fine team move by firing Hector Bellerin's cross into the roof of the net.
While CSKA were unable to cope with pace and panache, they exposed the north Londoners' defensive frailties.
Aleksandr Golovin levelled after 15 minutes. He curled home a free kick from 25 metres. His strike nestling in the right hand corner past the despairing dive of Arsenal goalkeeper Petr Cech.
But two goals in five minutes gave Arsenal the ascendance. Lacazette converted a penalty in the 23rd mintues after referee Pavel Kralovec deemed Georgi Schennikov had fouled Mesut Ozil in the area.
An Ozil cross from the left then paved the way for Ramsey to double his tally. The 27-year-old did it in style with an audacious flick over goalkepper Igor Akinfeev with the outside of his right foot.
Ozil was again the creator when Lacazette scored his his second with a rasping left foot shot past Akinfeev into the right hand corner.
Elsewhere in the competition Lazio beat Salzburg 4-2 while France international striker Antoine Griezmann claimed his 24th goal of the season in Atletico Madrid's 2-0 victory over Sporting Lisbon.
The Germany striker Timo Werner scored the only goal of hte game as RB Leipzig edged past Marseille.