Ronaldo's six years at Old Trafford saw him rise from an unknown midfielder from Sporting Lisbon to one of the world's most lethal players before moving on to Real Madrid for a world transfer record of £80 million in 2009.
Despite breaking goalscoring records and finding success at Santiago Bernabeu, Ronaldo revealed that he still misses his former side.
Speaking to Zoo magazine, he said: "I speak with Sir Alex sometimes and of course I miss Manchester.
"It felt like I left a family back there because I spent six years with all those guys and I still have a very good relationship with Ferguson and the rest of the lads.
"I still speak with Rio Ferdinand, Nani, Anderson and Patrice Evra. I still see them as a big family, so of course I miss them.
"I especially miss the apple crumble and custard they served at Carrington after training - it was amazing!"
Asked what he particularly missed about working under Fergie, Ronaldo joked: "Ha! I miss his good moods all the time! Always happy. But he always had a good energy around the players and the team - and I miss that."
Ronaldo also insists that he has grown as a player since his United days, but recognises his Champions League win with the Red Devils as one of his many highlights as a player.
He added: "I'm enjoying my football so much at the moment and I think I'm much better now than when I was younger.
"The best moments of my career so far have been when I won the Champions League with Manchester United and when I won my first title here with Real Madrid.
"And when I won the best player in the world, the Golden Boot - those were all special moments for me. Of course, I have many regrets and not just on the pitch, either. But I always try and improve myself.
"When I do something good, I carry on doing that and when I make mistakes I try to change them. I never regret making mistakes because I like to learn from them on and off the pitch.
"Last season I scored 40 goals and now the fans expect me to score more. That's a lot of pressure but I always try to improve on the last year."
The explosive attacker is expected to be one of the major stars to watch in this summer's Euro 2012 tournament and he believes Portugal can pull through a difficult group which includes Germany and Holland.
"My expectations for Portugal in the Euros are high because it's a great competition," he added.
"We are in a very hard group and it will be tough to beat Germany and Holland but I think it will be possible for us to go forward."