Ronaldo scored twice in the 3-1 Champions League round 16 first-leg win on Wednesday night.
Butragueno said: "To produce a good game to qualify, with that encouragement from the stands is less difficult for our players, Cristiano once again, has scored two goals ... to have a player with this scoring capacity and such competitiveness is a privilege."
El Vulture also spoke of Marco Asensio, who came off the bench to produce two late assists.
"He has read the match very well, they had a very advanced defence and he was able to get behind them, also with the help of Gareth [Bale]. The last two goals have come for him, his contribution has been very important."