River, 85-37 ahead of Racing in 164 league meetings dating back more than 100 years, fell behind to a 35th minute strike by the visitors' brilliant young Colombian playmaker Giovanni Moreno for his third goal in two matches.
Racing had the better of the first half at a nearly full Monumental but River, fighting to improve their poor relegation average, just about deserved the point after their fifth consecutive draw and sixth match without a victory.
Coach Angel Cappa's half-time adjustments included taking off veteran Ariel Ortega and sending on Buonanotte, who in December was driving a car that crashed killing three boyhood friends.
The 22-year-old vindicated the substitution when he had been on the pitch less than a minute, turning the defence to rifle a low left-footed shot from the right inside the near post.
It was nearly identical to Moreno's opener. The Colombian also turned a marker on the right side of the box and swiveled to shoot left-footed, but inside the far post of the same goal.
Relegation in the Argentine top flight is decided on the average points of a team over three seasons. River Plate, at the moment, occupy a promotion playoff berth.
Friday night's top-of-the-table clash at Velez Sarsfield ended in a 0-0 stalemate with Estudiantes remaining three points clear of their hosts with seven matches to go in the Apertura championship, first of two in the 2010/11 season.
Estudiantes have 27 points, Velez 24 and Arsenal 23 after they let slip a chance to move in on the leaders when they were beaten 3-1 at home by Godoy Cruz in Friday's other match. Godoy River have 18 points and Racing 17.
