Gwen Stefani Debuts Emotional Single 'Used to Love You' After Split from Gavin Rossdale

Gwen Stefani is pouring her heart into new music in the wake of her split from Gavin Rossdale.

The singer, 46, debuted her emotional new single “Used to Love You” during her MasterCard Priceless Surprises concert in New York City on Saturday.

“I just want to share a song that I wrote recently,” Stefani told fans before singing the powerful number. “This song is really special.”

As Stefani belted out her personal lyrics, including “I thought I was the best thing that ever happened to you” and “I guess nobody taught you how to love,” an intimate clip of her played in the background.

“Used to Love You” was produced by J.R. Rotem, a source close to the star confirms. The song and video were released Tuesday.

“[It’s] just truth,” Stefani told PEOPLE last month about an overall theme for her new music. “Just being clear and being true to myself. I just want to be fulfilled.”

Stefani and Rossdale – parents to Kingston, 9, Zuma, 7, and Apollo, 19 months – announced their divorce in August after 20 years together and nearly 13 years of marriage.

“While the two of us have come to the mutual decision that we will no longer be partners in marriage, we remain partners in parenthood and are committed to jointly raising our three sons in a happy and healthy environment,” they told PEOPLE in a statement.

In the months since, Stefani has been hitting the recording studio and returned to NBC’s The Voice, on which she serves as a judge alongside Blake Shelton, Adam Levine and Pharrell.

The No Doubt frontwoman celebrated her 46th birthday on Oct. 3. Her famous friends from the music competition made the milestone even sweeter by singing her praises in a loving video.

• Additional reporting by SARAH MICHAUD