The Brazilian, who played for nine different clubs in his own country without settling at any of them before moving to Portugal in 2009, put the Eagles ahead in the eleventh minute after a mistake in the Coimbra defence.
The 30-year-old struck again just before the half hour after Coimbra defender Marcelo Goiano failed to cut out Lazar Markovic's cross.
Argentine Enzo Perez completed the scoring in the second half, finishing off a move which he started himself by winning possession in midfield.
"We didn't expect such a poor and weak exhibition," said angry Coimbra coach Sergio Conceicao, whose team have beaten Porto and held Sporting this season.
"The three Benfica goals were inconceivable in top level competition and we also gave them other chances.
We surpassed ourselves against Porto and Sporting because we had ambition, soul and organisation. We didn't have any of that today."
Benfica, who last won the title in 2010, have 61 points from 24 games and stayed seven clear of Sporting who won 3-1 at Maritimo on Saturday.
Porto, champions for the last three seasons, needed a late goal from Colombian midfielder Juan Quintero to beat bottom club Belenenses who played the entire second half with 10 men after Joao Afonso was sent off for a foul on Jackson Martinez.
- Sports & Recreation
- Lazar Markovic