It was Bernardo's charitable contribution that undid Middlesbrough's worthy cause early in the second half at White Hart Lane, the defender giving away a penalty that Harry Kane gratefully scored.
One goal proved to be all that was needed to get the job done, with the toothless visitors ill-equipped to trouble fit-again Tottenham goalkeeper Hugo Lloris. Marten de Roon - scorer of a late equaliser in the dramatic 1-1 draw away to Manchester City in November - dragged Boro's best chance wide in injury time.
The victory sees second-placed Spurs, who had drawn at Sunderland and Manchester City in their previous two leagues outings, stay nine points behind Chelsea, the runaway leaders having briefly extended their advantage thanks to a dominant 3-1 win at home to Arsenal in the early kick-off.
Mauricio Pochettino's team will now focus on their trip to spluttering Liverpool on Saturday, while Middlesbrough remain just one point outside the relegation zone, with a home game against Everton coming up next weekend.
A hectic start to the game produced chances at both ends, Alvaro Negredo heading over the bar in the fourth minute after Adama Traore did well to get past Toby Alderweireld and swing a dangerous cross into the area.
Tottenham responded by pouring forward, Dele Alli finding Son Heung-min in space and the South Korea international drawing a smart save from Victor Valdes.
Ben Davies then sent an inviting delivery across the face of goal that Kane could not get to and Alli shot narrowly wide of the near post from Christian Eriksen's clever pass, as Spurs laid siege to the Middlesbrough goal in a four-minute spell.
Valdes, though, was fortunate the match officials did not spot his confrontation with Alli, the Spanish goalkeeper appearing to raise his hands to the face of the England midfielder.
The visitors successfully weathered that early storm and it took until the 25th minute for Tottenham to trouble them again, when Alderweireld met Eriksen's corner to head against the post.
With 10 minutes remaining in the half, Kane headed just over from a Son cross after some lovely football in the build-up, including a one-touch Alli pass to free the former Bayer Leverkusen man down the left.
The onslaught continued in the second half and Spurs were finally rewarded for their persistence in the 58th minute. Bernardo felled Son inside the area, leaving it for Kane to stroke home the opener from the spot.
Spurs enjoyed chances to extend their lead, Eriksen and Son - who caused Calum Chambers continual problems down Tottenham's left flank - both calling Valdes into action.
Despite Aitor Karanka throwing on Patrick Bamford with 11 minutes to go, Middlesbrough continued to toil without reward in the Tottenham half, De Roon dragging a good chance wide in injury time to sum up his team's attacking travails.