Taylor Hicks managed it, with “Do I Make You Proud”.
Bruno Mars, with “Just The Way You Are”.
Player, with “Baby Come Back”.
Clay Aiken, with “This Is The Night”.
Jason Derulo, with “Whatcha Say”.
The Teddy Bears, with “To Know Him Is To Love Him”.
Magic!, with “Rude”.
D4L - Laffy Taffy.
Per wiki, Mark Dinning’s debut single, “Teen Angel”, went on to reach #1 on the U.S. Billboard Hot 100 (February 1960) and number thirty-seven in the UK Singles Chart (even though it was banned from being played by the BBC).
Captain & Tennille managed it with “Love Will Keep Us Together”.
Lesley Gore, with “It’s My Party”.
Gregory Abbott, with “Shake You Down”.
Snow, with “Informer”.
Del Shannon, with “Runaway”.
Maureen McGovern, with “The Morning After”.
The Essex, with “Easier Said Than Done”.
Carrie Underwood, with “Inside Your Heaven”.
Alan O’Day, with “Undercover Angel”. O’Day had also composed “Angie Baby”, a #1 hit for Helen Reddy. The success of these two songs means O’Day is among the few singer / songwriters who wrote a chart-topper for themselves and one for another artist. (And he wrote a Top 40 hit for Cher, and for Bobby Sherman, and for The Righteous Brothers…)