Kaka returned from a six-week injury lay-off for the trip to La Romareda and ended up being his side's hero as he climbed off the bench to fire home the clinching goal in a 2-1 win with eight minutes to go.
The Brazil international has found himself under fire in some sections this season for his performances since joining for £56million last summer and also during his recovery from injury, with accusations his sights may have been set more on the World Cup than on Madrid's title bid.
However, Kaka said following the Zaragoza victory: "I'm very happy, it's been a very special night for me after many criticisms. The best answer is on the pitch.
"I've spent many years in the world of football, but the worst is that they doubt my injury. I only ask that the fans don't doubt my injury.
"I've felt very sad recently for the things that have been said about me. It's not true that I refused to take medication, delaying my recovery, because I've taken medication to play in this game.
"Also, it's not true I was thinking of Brazil and the World Cup. Right now I'm focused on Madrid."
Kaka's appearance against Zaragoza was his first since Madrid's Champions League exit to Lyon on March 10, but the capital club will now be hoping he is available for the final four games of the season against Osasuna, Real Mallorca, Athletic Bilbao and Malaga.
Kaka added: "I'm much better, but I still have to continue working. I had 15 or 20 minutes (against Zaragoza) and little by little I'm improving my fitness. The most important thing of all though was the victory."