Second half tries by Adam Powell and Chris Czekaj plus 10 points via the boot of outside half Gareth Davies were enough to see Cardiff secure their first title for nine years.
Ponty proved stern opposition for the home side and were eager to improve on their disappointing defeat to Bedwas last Saturday.
The Valley Commandoes were good value for their lead at halftime. Left wing Chris Clayton finished off two tries, the first from a well executed move and the second from an intercept. Full-back Kristian Baller converted both tries.
In between Ponty's touchdowns Cardiff's scrum half Andy Williams showed a clean pair of heals when he broke free from a ruck and sped down the blindside to score a well taken individual try. Gareth Davies chipped over the conversion but the visitors had the last say in the first spell when Baller put a penalty through the posts.
Cardiff reduced the arrears to just three points when No8 Adam Powell scored a converted try however just as it seemed the home side were getting back into the game, Ponty edged further ahead with a try to hard working flanker Rhys Lloyd to give the visitors a shock 22-14 lead.
Davies chipped away at the lead with a penalty before Welsh international winger Chris Czekaj crossed the whitewash. Davies's conversion put Cardiff in front for the first time of the match and he sealed a famous comeback victory with a well struck penalty to send the champagne corks popping.