Simon says / Lori Foster.

Enhanced descriptions from Syndetics:

From the New York Times bestselling author of the Ultimate series, a former MMA fighter returns to the ring while a beautiful investigator watches his every move...

With his perfectly chiseled, lava-hot body, Simon Evans, ex-fighter, also has a perfect life-great job, great girl, and more than enough dough. All that changes, though, when he catches his girlfriend cheating. To shake things up, Simon goes full-force back into the ring, ready to take out his rage on his opponents...

To make matters worse, the father who walked out on Simon and his mom eons ago wants to be back in the picture. He's hired his stepdaughter, Dakota, to find Simon. Hot on Simon's heels, the gutsy P.I. puts love on the back burner. But when attempts are made on Dakota's life, Simon steps in to protect her, all but putting both their hearts on the line...