Selena Gomez -- Sending Signals ... 'Memba This, Justin? (PHOTO)

Selena Gomez is heaping praise on Justin Bieber, and dayummm if she's not looking hot enough to suck the guy right back to her.

All the right parts of Selena were showing as she strutted out of her London performance in a revealing gown Thursday night. She recently said the ups and downs of her relationship with Justin were the fuel for her new album, "Revival."

And seemingly referring to his comeback, she gushed ... "This is what I always saw in him."

Listen up, Justin -- and more importantly ... LOOK, man!