They had the bonus point chalked up by the 35th minute, with 12 further points coming from the boot of out-half Ian Humphreys.
The hosts were held scoreless in the second period as Benetton Treviso, who did the double over Aironi over the festive period, came more and more into the game.
Lock Gonzalo Padro helped himself to a try, and out-half Willem de Waal kicked eight points for the Italians who were held up over the try-line in the dying minutes.
de Waal opened the scoring in the fifth minute, before Humphreys, on his return from an ankle injury, continued his recent run of strong kicking displays.
He converted five of his six place-kicks in a dominant first half from Ulster, who ran out 19-9 winners when the sides met at Stadio di Monigo in November.
In the rematch, Ulster grabbed their first try in the 12th minute, profiting initially from some strong running from Andrew Trimble. Willie Faloon and Best kept the move going before the ball was transferred to scrum half Pienaar who had the pace to make the try-line.
Humphreys converted and then swapped penalties with de Waal, with the Ulster number 10's penalty hitting the post before going over. Treviso full-back Chris Burton was narrowly wide with a drop goal attempt shortly afterwards.
Try number two arrived for Ulster in the 24th minute. Full-back D'Arcy linked with Spence who booted the ball forward and did well to gather it and score. Humphreys supplied the conversion for a 20-6 scoreline.
A defensively solid Ulster were beginning to find regular holes in the Treviso rearguard.
Five minutes after Spence's score, Trimble made a great break through the middle and passed for Pienaar to dash towards the line. He was hauled down just short, but quickly freed up the ball for D'Arcy to nab his second league try.
Humphreys maintained his 100% kicking performance before the bonus point was secured five minutes before the break. The Ulster forwards engineered a lineout drive from which Best muscled over for a try that television match official Marshall Kilgore confirmed.
Humphreys' first missed kick of the night failed to take the gloss off an impressive opening 40 minutes from the Ulstermen, who managed to keep Treviso at bay as the likes of Padro and Marco Filippucci stood out during a sustained period of pressure in the hosts' 22.
32-6 in arrears, Treviso opened the second half in good stead and touched down through Padro in the 49th minute. He rumbled over from close range, with Kilgore confirming the grounding, and de Waal added the extras.
Ulster looked dangerous again when Tom Court collected a loose ball and dashed forward to offload to the supporting Dan Tuohy, with Spence and the fit-again Stephen Ferris, who came on as a replacement, also getting ball in hand.
However, Ulster's second half endeavour went unrewarded as Treviso showed improved defence and discipline and moved the ball well in search of a second try.
It did not come though, with a dropped ball after a spritely counter and then replacement Franco Sbaraglini was denied by Tuohy's last-ditch challenge.
Ulster were outfoxed by a short lineout from Treviso and it seemed certain that they would make the corner. But Sbaraglini was held up and the hosts stood firm as time ran out on this spirited Treviso side.
Speaking after the game, Ulster coach Brian McLaughlin said: "It was very difficult to keep the momentum going after a brilliant first half. We had the bonus point in the bag at half-time but we defended well in the second half.
"We still have plenty to work on and we have a huge European game coming up next week - they don't come any bigger than Biarritz at home.
"We'll be up for it and we want to show the same intensity as we did in the first half."
|Ulster Rugby Score Card|
|Benetton Treviso Score Card|
|Willem de Waal||1||2||8|