The striker, who won the spot-kick after tangling with Eggert Jonsson, had his effort from 12 yards saved by Marian Kello in the 61st minute.
Despite the lack of goals, both sets of fans were treated to a high-tempo clash that swung from end to end.
In a frenetic start to proceedings, neither side was able to stamp their authority with much of the battle taking place in the middle of the park.
The home supporters made their feelings known to Andy Webster as every touch from the former Hearts defender was greeted with a cacophony of boos.
Webster was making his first appearance back at Tynecastle since controversially using a little-known FIFA rule to quit the club in summer 2006.
The first chance of the game arrived in the 15th minute when United striker Jon Daly fed Craig Conway in the box but the midfielder dragged a tame shot wide.
Moments later, Hearts midfielder Ruben Palazuelos headed Craig Thomson's corner off target at the near post.
Diminutive Hearts strikers Scott Robinson and Jamie Mole were not having much luck with high balls up against Webster and Kenneth but that did not deter the hosts from using that tactic.
United, meanwhile, showed greater ingenuity in the final third as Scott Robertson flashed Damien Casalinuovo's knock down wide from 18 yards on the half hour mark.
Hearts were forced into a sub two minutes later as David Obua hobbled off to be replaced by Arvydas Novikovas.
United midfielder Robertson was involved again in the 34th minute when his left-footed shot was well blocked by Kello.
The goalkeeper cleared the loose ball before Daly's arrival and picked up a painful knock that required treatment.
Hearts manager Csaba Laszlo and the Jambos fans were furious with referee Euan Norris' decision making as several awards did not go their way.
Norris was the fourth official in Hearts' stormy defeat at Hamilton last week that saw three players sent off in the tunnel following a post-match fracas.
Hearts survived a scare in first-half stoppage time when Daly's header from Craig Conway's free-kick came back off the post.
United striker Casalinuovo was replaced minutes after the restart as Cadamarteri was given the chance to impress.
In a lively start to the second period, Hearts full-back Lee Wallace's cross found Laryea Kingston at the back post but the Ghanaian's volley was well blocked by Paul Dixon.
Hearts then made a change of their own with Christian Nade replacing Mole.
United missed a great chance to take the lead in the 61st minute when substitute Cadamarteri's penalty was saved by goalkeeper Kello.
The former Everton forward won the foul in the box himself after racing past Jose Goncalves and tangling with Eggert Jonsson.
However, he failed to make the most from 12 yards as Kello got down to his weak shot.
Scott Robinson wriggled free for Hearts on the edge of the box but his shot sailed over the bar.
At the other end, substitute Danny Swanson's effort from 18 yards was well held by Kello.
The pace of the game remained high as both sides contributed to a hard-fought match.
In a well-worked move on the edge of the area, Michael Stewart dummied a pass to allow Nade to shoot but his effort was blocked.
Hearts had to play the remaining five minutes with 10 men after Kingston went off injured with the hosts having used their full quota of subs.
The home supporters booed the midfielder, who has been accused of not being fully committed to the club this season by manager Laszlo.