The WitchSlayer by Opal Reyne

When Amalia’s cat brought home a strange flying lizard during a terrible storm, she had no idea that it was a Dragon. Or that he would save her from burning at the stake, only to imprison her in his lair when she saw his human face. Now she is stuck in this cave with a moody, hot-tempered, and arrogant warrior – one who has killed her kind by the dozens.
She expected to feel trapped, but he somehow makes her feel unbelievably… safe.
Rurik’s only goal is to kill the Dark Witch, Strolguil the Vast. He never expected to find himself in a White Witch’s home in need of healing, or that she would be completely oblivious about his kind, or her own. He intends to abandon her, a lowly Witch, to her fiery fate, but he can’t ignore his blood-debt after she saves him.
Nor can he ignore the fierce desire that she grows in him when she roams free inside his lair.
However, there are Dark Witches afoot, and Rurik isn’t sure if he can shed years of hatred to trust the enchanting woman he has in his keeping.