Portugal forward Ronaldo struck in each half either side of a Mesut Ozil effort to keep Real hard on the heels of champions Barca, who had stretched their lead to five with Sunday's 2-1 home win over promoted Levante.
Real coach Jose Mourinho gave midfielder Kaka a run-out in the final 15 minutes for the Brazil playmaker's first appearance this season following post-World Cup knee surgery.
Di Maria played Ozil through for Real's second in the 19th before Dani Parejo dribbled past Alvaro Arbeloa and Lassana Diarra and lashed a shot past Real's Iker Casillas 10 minutes later.
Ronaldo looked to have made the game safe 12 minutes into the second half with a smart finish from Karim Benzema's pass, which put him two goals clear of Barca forward Lionel Messi on the La Liga scoring charts.
"Usually we are much more concentrated, much more compact and we gave our opponent a lot of space," the Portuguese said. "My team needs to defend better and I didn't like them much today."
In Monday's earlier kick-offs, Jose Catala and Borja Valero grabbed the goals as Villarreal cemented their grip on third, while Atletico Madrid missed the chance to climb above Espanyol into fifth when they were held 0-0 at home by Racing Santander.
