"Moon Tiara Stardust" is an attack that only appears in episode 5 of the anime series. As episode 5 was cut from the DiC dub, this attack is exclusive to the original and Viz Media versions of the series.
Usagi was reluctant to attack Iguara out of fear she would hit Shingo and other children, who were zombified by the Chanela. Luna suggested she use this attack instead, which was essentially Moon Tiara Action with a healing effect.
The attack was the same as Moon Tiara Action, except for its ending: instead of hitting its target, Moon Tiara Stardust would rotate above them in a circle, sprinkling sparkling dust on them; this dust reversed the zombified effects caused by the Chanelas.
This was technically Usagi's first healing maneuver, appearing long before Moon Healing Escalation.