Ronaldo made it 199 goals for Real Madrid in less than four seasons as two towering headers helped earn an entertaining 4-3 win over Valladolid.
The hosts bounced back from their Champions League elimination at the hands of Borussia Dortmund to keep the Primera Division title race alive for one more weekend at least.
He helped the hosts recover from conceding an early goal to Oscar, making it 2-1 after Angel Di Maria had levelled.
Javi Guerra equalised before the break for the visitors, but second-half efforts from Kaka and Ronaldo looked to have got Madrid home and dry.
Sastre's brilliant volley got Valladolid a late third, but there was no dramatic equaliser.