Guimaraes cruised to a convincing 4-0 win over Croatian side Rijeka to go top of Group I.
Abdoulaye Ba opened the scoring nine minutes before the break and Nii Plange effectively settled the tie with a second just after the interval before Moussa Maazou grabbed the third from the penalty spot.
Felipe Andre Andre completed the rout nine minutes from time to fully reflect the home side's dominance in front of a crowd of 12,000.
The visitors had the first real attempt on goal after eight minutes but defender Andre Paulo Oliveira got in the way of Leon Benko's shot and the danger was cleared.
Plange and Filipe Andre Santos then tested Rijeka goalkeeper Ivan Vargic before Ba found the back of the net by getting on the end of Chris Malonga Ntsayi's corner from the right.
That was the only goal of the first half but it did not take long for the home side to double their lead when play resumed, Maazou setting up Plange to finish confidently with his right foot.
Rijeka never looked capable of getting back into the game and any faint hopes they had disappeared in the 68th minute when Luka Maric was penalised for a a foul on Andre Andre and Maazou converted the resulting penalty.
Vargic had to make several more saves before eventually conceding a fourth goal, Andre Andre slotting home right-footed on in the 81st minute to ensure the Portuguese side's dominance of possession - they had 68 per cent over the 90 minutes - did not go to waste.