When mentor Simon Cowell introduced Melanie Amaro to 'X Factor' this week, he simply said, "We've saved the best for last." When Amaro hit the first note of Michael Jackson's 'Earth Song,' she proved him right.

Amaro is no stranger to the King of Pop's catalog, having already performed 'Man in the Mirror' and 'Will You Be There' on the show -- two power ballads, which is where she knows she shines. Cowell, accused of playing it safe with protege Drew this week, chose to take a gamble with Amaro for this performance. "I don't want you to be good, I want you to be incredible," Cowell said. "This is a big deal for her, but you have to take risks sometimes."

'Earth Song' was a tall order. The original incorporates elements of opera, gospel and blues -- and wasn't released as a single in the United States, so it was less likely to register with viewers and voters if Amaro's performance was less than stellar. "This is one of Michael's best songs," Cowell said of the tune (which was a hit in his native U.K.), "but one you do not touch."

At this point, anything we write about Amaro's vocals is trite. The girl is without a doubt the best vocalist in the competition, even on her worst day -- which certainly wasn't this week. Backed by flashing images of natural disasters and devastation, Amaro, though out of her comfort zone, knocked it out of the park, earning unanimous praise from the panel.

"For one second I forgot we were in a competition, and I felt like we were at a Melanie Amaro concert," L.A. Reid said. "You were amazing and maybe the best of the night." He couldn't resist teasing Cowell, though. "I'm sure it had nothing to do with Simon," Reid chuckled, "but it was good."

Over 30's judge Nicole Scherzinger loved it even more than Reid. "Not only was that the best of night, but maybe the best of the entire show," Scherzinger gushed. "If that performance doesn't save a small country somewhere, I don't know what will."

Paula Abdul kept her typically enthusiastic response atypically brief. "It was flawless, you looked gorgeous, and you nailed it."

For the first time all night, Cowell agreed with his panel. "I could not be more proud," he began, "And for all of us, including the Jackson family here tonight -- I can't think of better way to pay tribute to him as an artist," he said firmly. "You were amazing."

Watch Melanie Amaro Perform 'Earth' on 'X Factor'