The Portuguese made a bad start by conceding a 15th minute penalty for a foul on Pedro Mosquera, with Edu Albacar sweeping the ball home past Keylor Navas making his official debut in the Real goal.
Gareth Bale quickly put Real back on track as he headed in a James Rodriguez cross five minutes later and then the referee pointed to the spot for a foul by Mosquera on Marcelo even though there was marginal contact.
Ronaldo fired in the 28th minute penalty and headed home a Marcelo cross four minutes later to extend Real’s lead.
He was then upended by Mario Pasalic with 10 minutes to go and slotted home his second spot-kick while there was still time for another goal from Ronaldo deep in injury time where he finished clinically in the box.
The World Player of the Year now has seven goals in four days after the hat-trick he scored on Saturday in the 8-2 win over Deportivo La Coruna.
While Real have played some brilliant football, they have looked vulnerable in defence and are three points behind La Liga leaders Barcelona who have 12 points and a game in hand. They play Malaga on Wednesday.
Champions Atletico have eight points from four games and play Almeria, also on Wednesday.
“I’ve managed to get four a few times before but this is all down to the team. Things are going for me and it is down to my team-mates who help me a lot,” Ronaldo told reporters at the Bernabeu.
“It was a good game for us. We started poorly, I gave away a penalty, but we responded well with two quick goals,” added the Portuguese.
Real coach Carlo Ancelotti made several changes for the fixture with 29-year-old Ronaldo the oldest player in a youthful-looking starting lineup.
Isco and Asier Illarramendi, who looked sharp when they came on against Deportivo, were rewarded by starts while Ronaldo and Bale were given more central roles in attack with Karim Benzema rested.
Ronaldo was unforgiving as he buried his first spot-kick of the evening into the top corner to put Real ahead and the home side then began to play the ball around with more confidence.
Elche concentrated on containing Real after the break but Ronaldo still added two more and Toni Kroos was inches away from scoring as well when his shot from inside the area came back off the crossbar.
Celta Vigo survived a late penalty scare in a 2-1 win over local rivals Deportivo La Coruna when Sergio Alvarez saved from midfielder Haris Medunjanin two minutes from time.
Joaquin Larrivey headed Celta in front midway through the second half after Isaac Cuenca had cancelled out Nolito’s early strike but Depor had the chance to equalise when Gustavo Cabral handled in the area.
Medunjanin’s spot-kick was heading for the corner but Alvarez got down to beat it away.
“It was a great moment for me but the most important thing was the win,” Alvarez told reporters. “It was a tough game as we expected and a good performance from us.” (Reuters)