Everton climbed back into fourth place in the Premier League after a comfortable win over Manchester City.
Joleon Lescott celebrates after scoring Everton's second goal
The Toffees could have had a penalty when Tim Cahill's shot hit Micah Richards' arm and also went close when Steven Pienaar's shot hit the post.
Yakubu put Everton ahead when he met Cahill's low cross and Joleon Lescott headed home a second soon after.
City lost their shape completely after the break and had Martin Petrov sent off late on for kicking Leon Osman.
It ended up as a ragged performance from the home side, with central-defender Richards pushed forward in the second half to leave some huge gaps at the back.
And, if Everton had taken their chances and referee Rob Styles had seen two other penalty claims differently, then this would have been an even more comprehensive victory for the Toffees.
City are also involved in what is becoming an intriguing race for the fourth and final Champions League spot but they now lie six points behind Everton after they were found horribly wanting here.
Yakubu, operating as a lone striker, went close to opening the scoring in the third minute when he beat Joe Hart to Pienaar's cross but saw Richard Dunne clear his weak shot off the line.
The visitors kept coming forward and should have had a spot-kick when Cahill's shot came back off Richards' elbow after the defender lost his footing in the area.
That stung City into action but they were unable to penetrate a solid Everton backline that defended fiercely on the edge of their own penalty area.
The same could not be said of the home defence, however, and Pienaar was given plenty of time to pick his spot before he curled in a dipping shot that came back off the woodwork with Hart beaten.
City's players, who were sent on holiday by manager Sven-Goran Eriksson after beating neighbours Manchester United in their last game on 10 February, looked as though their minds were still on the beach.
Everton finally capitalised on the half-hour mark when Dunne gave the ball away and Cahill crossed for Yakubu, who finished with aplomb.
Things got worse for City before the break when Lescott escaped Dunne to meet Carsley's cross and head past a stranded Hart.
That still left time for Eriksson's men to get back into the game but the second half only served to further expose their shortcomings.
Phil Neville was unlucky to see his shot fly over the bar straight after the interval and Dunne had to clear off the line after Cahill met Yakubu's cross.
Eriksson's response was to throw men forward but although Petrov had a shot blocked by the impressive Phil Jagielka and Dunne headed over, City were looking even more shambolic at the other end.
Richards was lucky to only concede a free-kick on the edge of the area when he handled Lescott's long throw and Nedum Onuoha also handled the ball inside the box without being penalised.
Hart saved City's blushes with a superb stop to keep out Lee Carsley's long-range shot, and repeated the trick to deny substitute Andy Johnson from close-range.
City did threaten again through Nery Castillo's long-range shot, which was blocked by Tim Howard, but their miserable night was summed up by Petrov's late dismissal after he kicked out at Osman, seconds after clashing with Yakubu.
Man City: Hart, Onuoha, Dunne, Richards, Ball, Vassell (Castillo 75), Gelson, Hamann (Elano 46), Ireland (Caicedo 68), Petrov, Mwaruwari.
Subs Not Used: Isaksson, Corluka.
Sent Off: Petrov (90).
Everton: Howard, Hibbert, Yobo, Jagielka, Lescott, Neville, Carsley, Osman, Pienaar (Fernandes 56), Cahill, Yakubu, Fernandes (Johnson 67).
Subs Not Used: Wessels, Nuno Valente, Anichebe.
Goals: Yakubu 30, Lescott 38.
Ref: Rob Styles (Hampshire).
BBC Sport Player Rater man of the match: Everton's Yakubu 8.00 (on 90 minutes).
Please note that you can still give the players marks out of 10 on BBC Sport's Player Rater after the match has finished.