His songwriting career got off to a quick start when he was signed to a publishing deal at age 19 and credited with co-writing Pop Idol winner Will Young's 2004 Top Five hit single "Your Game," the recipient of the 2005 Brit Award for Best British Single.
In the wake of this success, Cruz made his debut as a solo artist in 2006 with the Top 30 single "I Just Wanna Know." Initially released by his own label, Rokstarr Music London (later renamed Rokstarr Entertainment Division), the song earned him a major-label recording contract with Island Records. Following a few more singles, "Moving On" and "Come on Girl," the latter of which hit the Top Five, Cruz made his full-length album debut in 2008 with Departure. Entirely written and produced by the singer/songwriter himself, Departure spawned another two singles, "I Can Be" and "She's Like a Star," and earned favorable reviews. Prior to releasing his second album, Cruz furthered his reputation as a hitmaking songwriter. In addition to co-writing songs for British pop superstars Cheryl Cole ("Stand Up") and JLS ("Keep You"), he penned material for grime rapper Tinchy Stryder's second album, 2009's Catch 22, in particular the Top Five hit "Take Me Back" and the chart-topping smash "Never Leave You."
"Break Your Heart," the lead single from Cruz's second solo album, Rokstarr, topped the U.K. singles chart in September 2009, a month after "Never Leave You" vacated the spot, and third single "Dirty Picture" was another major hit, reaching the Top Ten. Produced and written in collaboration with fellow U.K. hitmaker Fraser T. Smith, Rokstarr was re-released internationally in 2010 with the addition of "Dynamite," a Dr. Luke production that topped the charts in a half-dozen different countries. (It also earned him three Billboard awards, and a pair of ASCAP awards.) "Break Your Heart" was likewise re-released internationally and hit number one in several different countries, including the United States, where it achieved a record-breaking jump in Billboard from number 53 to the top spot in one week.