Catania thrashed Palermo 4-0 in the clash of the two Sicilian teams while Alessandro Matri continued his impressive form for Juventus, scoring his sixth goal since joining them at the end of January in the 2-0 win at AS Roma.
Napoli stayed three points behind leaders AC Milan, who have 65 points from 31 games after Saturday's 3-0 win over Inter, and moved above the defending champions.
Uruguay striker Cavani took his Serie A tally to 25 goals, level with Udinese's Antonio de Natale, as Napoli kept alive their scudetto hopes in a fiery match which left the visitors fuming at three key decisions.
Lazio appeared to have a goal wrongly disallowed with the score at 2-2 when Cristian Brocchi's long-range effort bounced down off the crossbar. Replays suggested it had crossed the line by at least a metre.
"You can see very well, it wasn't a case of five centimetres over the line, it was very evident that it went in, there's no way you can consider that it was not a goal," said Lazio president Claudio Lotito.
The visitors, who stayed fifth in the table two points behind Udinese in the Champions League qualifying round spot, were also angry with the Napoli penalty which made it 3-3 and said Napoli's winner came from an offside position.
It did not seem to matter when Brazilian defender Andre Dias doubled Lazio's lead in the 57th minute, sticking out his foot to volley in from Javier Garrido's whipped free-kick.
That was followed by the Brocchi incident, Lazio's protests barely subsiding before they were gifted the lead when Salvatore Aronica turned the ball into his own goal from close range.
Cavani and Giuseppe Sculli were booked for an ugly exchange which led to a mini-brawl in stoppage-time and the Uruguayan was lucky not to be sent off for diving seconds later. "We were born to suffer," said Napoli coach Walter Mazzarri.
"At one point it seemed that we were jinxed, but we managed to turn things around.
"We complicate life and we need to improve from this point of view but with football, determ
