Ronaldo hadn’t scored for Juventus since the start of the month. He came close on a couple of occasions before breaking the deadlock in the 38th minute when he headed in an Alex Sandro cross.
Serie A: Zlatan Ibrahimovic nets 500th club goal to help AC Milan beat Crotone; Lazio win against Cagliari
Ibrahimovic reached the landmark in 825 games, having made his professional debut for Swedish club Malmo in 1999.
Second-placed Inter stay one point behind Serie A leaders AC Milan who host champions Juventus later on Wednesday.
Martinez and Romelu Lukaku proved decisive for the northeners, the strike duo being involved in five of Inter's goals.
Juventus had to play most of the match at a numerical disadvantage after former Fiorentina winger Juan Cuadrado was sent off in the 18th minute.
Serie A: Cristiano Ronaldo's twin strike helps Juventus inflict 4-0 loss on Parma, inch closer to leaders AC Milan
Ronaldo, who missed a penalty in the midweek 1-1 draw with Atalanta, made amends with his third brace in four games.
Manuel Lazzari scored an own-goal and Lazio gifted Adrien Tameze the winner in Rome. Felipe Caicedo had equalized for the capital side early in the second half.
Serie A: Cristiano Ronaldo's brace helps Juventus beat Cagliari; Lazio edge Crotone on Ciro Immobile's return
Lazio also won 2-0 under torrential rain at Crotone, but Atalanta were held 0-0 at promoted Spezia days before their Champions League trip to Liverpool.
Serie A: Inter Milan left furious by contentious VAR decision during draw against Parma; Atalanta beat Crotone
Inter had a strong penalty appeal when Botond Balogh hauled down Ivan Perisic in the second half, with Conte skipping his press conference, apparently in protest at the decision.
Serie A: Zlatan Ibrahimovic scores brace as AC Milan clinch derby win against Inter; Napoli thrash Atalanta
Milan won their opening four matches for the first time since the 1995-1996 season when they won the title under Fabio Capello.
Spezia were founded in 1906 and last played in Italy's first division in the 1920s, before the Serie A was formed.
With only two games still to play, Atalanta moved within five points of Juventus, which can clinch a record-extending ninth straight title on Sunday by beating Sampdoria.
Serie A: Napoli hit back twice against Udinese to keep title hopes alive as leaders Juventus drop points
Napoli kept their title hopes alive with a 4-2 win over Udinese on Wednesday as champions Juventus' path to a seventh consecutive Serie A title was stalled 1-1 at Crotone.
Serie A: Paulo Dybala's brace takes Juventus past Verona; Benevento claim their first-ever victory in Italy's top league
Blaise Matuidi had put Juventus ahead after just six minutes but it took Dybala to unlock the victory after the hosts hit back through former Juventus player Martin Caceres on 59 minutes.
Inter are second, two points adrift of leaders Napoli who travel to Udinese on Sunday, with champions Juventus four points off the leaders in third before hosting Crotone.
Crotone manager Davide Nicola's journey after guiding his team to safety in memory of his son is one of the nominees for November’s Laureus Best Sporting Moment.
As Laureus World Sports Awards' India partners, Firstpost brings you the November nominees for the 2018 edition:
Inter Milan ended Napoli's winning streak in Serie A with a goalless draw despite a hard-fought top of the table clash in Naples on Saturday.
Dybala's heroics helped Juve bounce back after their 3-0 Champions League flop in Barcelona.
The win in Calabria allowed Luciano Spalletti's Inter Milan to position themselves among the title challengers alongside champions Juventus and Napoli, who will also bid to make it four out of four on Sunday.