His Ward by Sam Crescent

The last thing scarred and reclusive Luca Brown wants is the guardianship of an eighteen-year-old girl. Now that his friend is dead, he’s the one that’s got to take charge of Mavis Miller. The only problem … she’s not a girl. From the first moment he sees Mavis, his reaction to her scares the shit out of him. He’s now responsible for her, and that means he shouldn’t be thinking about her in anyway at all.
Mavis has never fitted in. Even her parents hated her and shipped her off to boarding school. Luca is different, and the scar on his face doesn’t scare her. After eighteen years of being ignored, she’s shocked when Luca takes her over his knee and punishes her for putting herself in danger. His touch. His hands. They drive her wild, and she wants him.

She’s the first woman to not flinch away. He should tell her no. He’s the guardian, but he doesn’t see her as his ward. No, he sees her as his, and he doesn’t want to just protect her—he wants to own her.