The leaders had been second best for much of the first half, but improved after the break and claimed all three points when the Argentine forward fired home from 15 yards.
Swansea built on a positive start to the game and registered eight attempts at goal in the opening 45 minutes, forcing home goalkeeper Tim Krul into several saves.
First the former Newcastle man palmed away Daniel James’ angled drive, then kept out George Byers’ long-range effort before clawing out Bersant Celina’s deflected 25-yard shot.
In contrast, Norwich struggled for openings, as top scorer Teemu Pukki dragged their best chance wide from 15 yards after racing on to Buendia’s pass.
But the Canaries’ only effort on target of the game nine minutes into the second half proved crucial as Buendia skipped past the challenge of Matt Grimes and rifled home a powerful left-footed effort past Kristoffer Nordfeldt.
Pukki went close to a second late on but saw his low shot come back off the post, forcing the Finn to wait in his bid to become the first Norwich player to score 25 league goals in a season since Chris Sutton in 1993.
Swansea, who were only able to name six substitutes after striker Oli McBurnie was forced to miss the game through illness, posed less of a threat after the break but went close to an equaliser when defender Mike van der Hoorn headed over from a corner.
However, Norwich held on to claim their sixth win in seven games to not only extend their lead over second-placed Leeds but also move seven points clear of Sheffield United in third.
The Blades host South Yorkshire rivals Rotherham United on Saturday, while Leeds travel to play-off chasing Bristol City.
Norwich boss Daniel Farke told BBC Radio Norfolk:
“It was a complicated game as Swansea were fantastic. They are by far the best team we have played in recent months.
“Our pressing in the first half was on the same level as recent games but wasn’t good enough because Swansea had many solutions and were able to bypass us.
“We had to change a few details at half-time and we were much better in the second half, so I’m pleased we were able to win and get a clean sheet.
“I am unbelievably happy we were able to handle this difficult task and that is my biggest joy. Tomorrow evening perhaps we will have a short look at the table and see what this result means.”
Swansea boss Graham Potter:
“It was a performance the players can be proud of.
“We were up against a good side who usually outscore teams convincingly, but we restricted them to very few opportunities and had a few chances ourselves.
“We were always in the game although we didn’t really do enough in the final third to get a result.
On McBurnie’s absence: “Oli felt ill when he came down here, there was a bit of fever and he was driven home today.
“For the first time since I have been here, we came down with just 18 players because we wanted to leave a few players back home with the midweek match against West Brom in mind.
“So we had to go with just six on the bench.”