Lamela created and scored the opening goal in the 50th minute and started the move that led to the second nine minutes later as River took their tally to four points from two matches in the Clausura championship.
The 18-year-old was at the heart of River's best moves, lighting up a match that seldom rose above the mediocre as both teams attempted to improve poor relegation averages.
Having started the move for the opener, he took a square pass on the left from Pavone and chipped the ball exquisitely over advancing goalkeeper Gaston Monzon for his first goal at River's Monumental stadium and third in 17 matches all told.
Seven years ago River, who had allowed Messi to slip through their grasp, agreed with the then 12-year-old Lamela's parents to pay him a monthly wage to stay and develop at the club rather than take up an offer to move to Barcelona.
River's arch-rivals Boca Juniors, tipped as title favourites, have three points after a 1-0 away win at Racing Club on Saturday helped them recover from the shock of a 4-1 defeat by Godoy Cruz at home last weekend.
