Brazilian striker Lima grabbed an early opener from the spot for the Lisbon club who knew a win would bring them closer to a 33rd league title, but Maritimo defender Igor Rossi equalised for the hosts.
Benfica came out strongly in the second half and Rossi turned villain for Maritimo when he deflected Eduardo Salvio's cross into his own net after 72 minutes.
"We became very anxious after the 1-0. I calmed the players down during the break and in the second half we played like champions," Benfica coach Jorge Jesus told Portuguese television SportTV.
Benfica have 73 points from 27 matches and Porto 69. The league leaders host Fenerbahce on Thursday in the second leg of their Europa League semi-final having lost 1-0 in the first leg in Istanbul last week.