Goals in each half from Adem Ljajic and Stevan Jovetic ensured a comprehensive win for Fiorentina against Inter in front of an ecstatic home crowd.
Fiorentina dominated the first half, rarely troubled by Inter's toothless attack, and it was only a fine display from keeper Samir Handanovic that kept the scoreline respectable.
Fiorentina took the lead in the 13th minute after Jovetic flicked a cross by Manuel Pasqual into the path of Ljajic who got in front of defender Juan Jesus to beat Handanovic with a neat diving header from close range.
Having denied Jovetic and Borja Valero in quick succession, the unfortunate Handanovic could do little about the home side's second.
Jovetic shrugged off the attentions of Andrea Ranocchia before curling in a fine shot from the left-hand side of the penalty area with the keeper rooted to the spot.
The Montenegrin got his second 10 minutes into the half, set up by a neat Alberto Aquilani back heel that left him free to hit a powerful right-foot shot past Handanovic.
Ljajic made it four in the 65th minute, given time by Inter's woeful defence to direct Borja Valero's pass towards the back of the net.
Antonio Cassano's late consolation aside, this was humiliating for Inter who face the remainder of the season without talismanic striker Diego Milito who will be sidelined by a knee ligament injury.
There were also leapfrogged by city rivals Milan who sit fourth in the standings, rejuvenated by former Nerazzurri player Mario Balotelli and with the Milanese derby looming next weekend.
Struggling Pescara lost 2-0 to Cagliari and Torino earned three points with a 2-1 home win over Atalanta.
Genoa, easing clear of the drop zone, saw off Udinese 1-0 and Catania are seventh thanks to a 1-0 win over Bologna. Siena host Lazio on Monday.