The Rabobank rider remains eight seconds behind the Manxman in the GC in the Netherlands race.
Cavendish led Team Sky team-mate Juan Antonio Flecha home on the 184km stage from Verviers. Flecha is at +14s in the overall standings.
Team Sky, in control of the peloton, were never more than four minutes behind an early breakaway of four riders featuring Nelson Oliveira (Radioshack Nissan Trek), Jaroslaw Marycz (Saxo Bank), Marco Haller (Katusha) and Dion Beukeboom (Cycling Team de Rijke - Shanks).
After the famous La Redoute climb at the halfway stage, Radioshack Nissan Trek pair Jan Bakelandts and Ben Hermans escaped the peloton and caught up with the front four.
Oliveira and Beukeboom were absorbed back into the peloton 50km from the end, with the front four 2:15 ahead at that point. Of them, Bakelandts then went out alone and found himself a minute clear with 10km remaining.
However they were all caught by the peloton before Boom claimed the final uphill sprint.