After a defensive blunder let Karim Benzema open for Madrid 18 minutes in, Ronaldo unleashed an unstoppable strike to double the advantage in the 26th. The former Manchester star then went on to find the back of the net twice more after halftime.
Ronaldo did his best to make amends for his own goal that cost Madrida loss at Granada in the last round with his 22nd, 23rd and 24th goals in the league this season. Only Barcelona's Lionel Messi, with 34, has scored more.
Apparently with the English champions in mind, Madrid coach Jose Mourinho left Xabi Alonso off his squad and fellow first-choice midfielders Mesut Oezil and Sami Khedira on the bench.
Instead, sparingly used Kaka got his first start since Dec. 4.
Madrid eased in front when Benzema was well positioned to take full advantage of a miscue by Sevilla's defense. Sevilla goalkeeper Antonio "Beto" Bastos deflected Ronaldo's low cross off teammate Fernando Navarro, and the ball fell for the France striker to nudge it over the goal-line.
Madrid kept the pressure on and Ronaldo made it 2-0 when he shimmied around Sevilla midfielder Hedwiges Maduro, put the ball on his left foot, and let loose a dipping shot from beyond the area that struck the net just inside the far upright.
Barely 30 seconds into the second half, Ronaldo made Sevilla defender Federico Fazio pay dearly for his sluggish response to reach a pass as he beat him to the ball and fired under the helpless Beto.
Ronaldo wasn't done and finished off a counterattack in the 59th that he had started from near his own area, racing forward to tap in Gonzalo Higuain's cross.
Four minutes after recording his 20th hat trick for Madrid — he scored one for Manchester — Ronaldo was substituted to a standing ovation by the Santiago Bernabeu crowd.
Higuain left Madrid with 10 men from the 66th after he picked up his second yellow card. Maduro followed suit for Sevilla in the 81st.
Defender Pepe went on for Madrid late for his first action since surgery on his right ankle in early January.
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