كتب : Hatem Maher
Skipper Shadi Mohamed broke the deadlock eight minutes past the hour mark from the penalty spot before playmaker Mohamed Abou-Treika marked his return from a three-month lay-off with a second nine minutes from time.
The Cairo giants advanced with 4-2 aggregate victory to continue their bid towards an unprecedented third successive Champions League title.
Ahli boss Manuel Jose included Abou-Treika in his starting line-up to support attacking duo Emad Meteb and Flavio Amado.
The South Africans succeeded in keeping Ahli strikers at bay through a successful offside trap in the first-half, however, they couldn't pose any threat on Ahli keeper Essam Al-Hadari.
The hosts had the first chance after seven minutes when Tunisian midfielder Anis Boujelbene stole the ball from a Sundowns defender in the right hand side of the area before providing a back pass to Meteb, whose low shot hit another player and went wide.
In the 20th minute, Meteb capitalized on a poor clearance by Sundowns keeper Calvin Marlin before cutting inside and curling a right-footed drive that deflected off a defender and went over the bar.
The Egypt international striker appealed for penalty 10 minutes after re-start when he was tugged inside the area but the referee waved play on.
Midfielder Mohamed Barakat brilliantly exchanged the ball with Flavio on the edge of the area in the 67th minute but his low shot was easily collected by Marlin.
Ahli were awarded a penalty one minute later when Barakat was struck in his knee by Benson Mhlongo's boot.
Skipper Shadi Mohamed stepped-up and successfully converted the ball into the back of the net despite Marlin's rightly-directed dive.
Sundowns striker Lerato Chabangu almost leveled the score in the 72nd minute after his shot deflected off Boujelbene and floated towards the net but Al-Hadari tipped it over.
Abou-Treika ensured the victory in the 81st minute after he latched on to Meteb's long ball before superbly chipping the ball into the far angle of the net from a tight angle.