Brazilian striker Jonas Oliveira opened the scoring with a wonderful low drive from 25 yards in the first half before Eliseu matched it with another strike from outside the box 15 minutes from time.
The champions subsequently stretch their lead at the top of the table to seven points, although Porto will reduce that deficit if they beat Arouca on Sunday.
Vitoria Setubal moved four points clear of the bottom two after ending a six-match winless league run with a 1-0 triumph at Vitoria Guimaraes.
Bruno Ribeiro's side claimed all three points from their trip to as Rambe scored the only goal of the game six minutes into the second half.
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